Tag: Security

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Visit us at it-sa 2024: Threats of Device Fingerprinting for Enterprises

What data is transferred by business apps, and how secure is their processing? Our research shows: If your employees use apps arbitrarily, you put your company’s security at risk.

At it-sa 2024, we present our app analysis framework Appicaptor. You can use it to automatically check whether apps are compliant with your company’s IT security demands. New results within the Athene funded research project FiDeReMA will improve Appicaptor analysis techniques. Among other things, the goal is to identify and evaluate privacy implications when using arbitrary apps.

Our current efforts to improve Appicaptor revolve around different privacy aspects:

  • Device fingerprinting
  • App DSGVO Consent Banners
  • Permission piggybacking of Android in app third-party libraries

Device Fingerprinting

Device fingerprinting is a technique used to uniquely identify devices and therewith typically also users. Mobile apps make use of different device properties such for example device name, software version and others. They combine such values mostly with a hashing function to a unique identifier. Use cases for device fingerprinting are app usage statistics, fraud detection and mostly targeted advertisement.

When employees install apps with device fingerprinting on their mobile corporate devices, it can lead to the loss of sensitive business data for companies. Attackers can acquire the collected data and potentially identify the devices of company management, spy on trade secrets, and ascertain customer contacts. In practice, the Cambridge Analytica case shows how sufficient data from various sources can be used to analyze users and manipulate them through targeted advertising, thereby influencing even election results.

Identified Device Fingerprinting Activity for the Top 1.000 Android Apps (source)

Our analysis results show that more than 60% of the top 1,000 apps on Google Play employ device fingerprinting techniques. This allows a unique device identification even across app borders.

We extracted 30,000 domains from the most popular 2,000 iOS and Android apps. Afterwards, we filtered out domain names for the most prevalent device fingerprinters covering 90% market share. We were able to prevent device fingerprinting in 40% of the cases by using publicly available domain blocklists. These lists are specialized on tracking and advertisement domains and can be easily applied to for example a firewall. Another 40% would easily be blockable by updating the blocklist: Some fingerprinters use random subdomains for their communication in the form of https://8726481.iFingerprinter.org giving many possibilities to be blocked.

We also proposed an approach to randomize return values of popular properties used for device fingerprinting. Our results prove that this technique dramatically reduces the uniqueness of the device fingerprint. Nevertheless, respective APIs remain accurate enough for their intended use cases. The hope is that our proposed techniques are included in future Android and iOS releases.

In-App DSGVO Consent Banners

Many of the previously mentioned device fingerprinting properties would typically require user consent as stated by the DSGVO. According to recent court decisions and EU regulations, rejecting must be just as easy as accepting consent banners. However, many companies don’t obey such regulations. Those who obey mostly apply dark pattern to push the user into accepting all tracking.

Example DSGVO Consent Banner with the option to reject all tracking on first instance.

We are currently working on detecting if apps provide a reject option on first instance, without having to click through several submenus. In our attempt, we are employing artificial intelligence to analyse such consent banners for reject options on first instance. The results yield a success rate of 82%. Some apps try hard to remain within legal boundaries but make it hard for users to reject data usage. Can you find the first level reject option in the following consent banner? – Yes there is an option.

Example DSGVO Consent Banner that uses dark patterns to hide reject tracking option.

We have collected the most interesting consent banners and bundled them into a game. With the app “Reject all cookies” you need to overcome several consent banners and keep your data private. Having rejected all “cookies” in the app you can win real cookies at our it-sa 2024 booth (6-314).

Permission piggybacking in Android Apps

Traditionally, Android apps comprise a main application and several supporting libraries. These libraries often inherit permissions from the main app, granting them unnecessary access beyond their core functions. This leads to permission piggybacking, where libraries exploit inherited permissions to gather data without requesting them directly. Advertisement and tracking libraries particularly leverage this tactic to collect extensive user data.

We have developed an analysis tool to detect third-party app libraries only probing for already granted permissions, without ever requesting permissions themselves.

Analysing the top 1,000 apps on Google Play reveals that 50% of the libraries exhibit this permission probing behaviour. Presumably, these libraries then adapt their behaviour according to the granted permissions of the main app. Accordingly, they collect more or less data, as available. Most of the identified libraries exhibiting such behaviour are well-known advertising and tracking libraries. This fact underlines the urge for a finer granular permission system to separate main app and third-party libraries.

Visit us at it-sa 2024 and have a cookie with us!

You’ll find us in hall 6, booth number 6-314 for a demonstration and discussions.

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Security Implications of Apple ID Switching and Keychain Merging in COPE Mobile Environments

The ability to switch Apple IDs on iOS devices poses a security risk for Corporate-Owned, Personally Enabled (COPE) mobile environments. When users opt to retain Keychain entries while transitioning from a corporate Apple ID to a private Apple ID, it results in the merging of passwords to the private Apple ID. This merging poses a significant challenge for organizations that need to maintain strict control over corporate credentials, as enterprise passwords can then be synced with all private devices using the private Apple ID.

Switching Apple IDs on an iOS device involves opening the “Settings” app on an iOS device, navigate to the Apple ID section and opt to sign out of the current Apple ID. This prompts a confirmation step, asking users if they wish to keep a copy of their data on the device or to delete it. This decision is crucial to consider because if the user opts to keep the Keychain data to be stored on the device, this decision will have implications for the passwords associated with the Apple ID currently signing out. Following the sign-out, users can proceed to sign in with the new Apple ID. Once the necessary information is entered and the setup is complete, the iOS device becomes associated with the new Apple ID. The device syncs with the new account, applying apps, data, and settings associated with the updated Apple ID. However, apps installed with the previous Apple ID are still usable.

Saved passwords of personal Apple ID
Saved passwords of corporate Apple ID

Keychain Merging and Its Effects

When logging into a website using Safari, a pop-up typically appears, asking if the user likes to store the password for AutoFill. This method simplifies the process of adding accounts to the password store. Alternatively, when creating a new account, users receive an automatically generated strong password. In either case, users can add accounts and passwords in the password store. The passwords are stored in the Keychain. If the user chooses to keep the Keychain data stored on the device during the Apple ID switching, this results in a merging of the stored passwords of the former and the latter configured Apple ID on the device.

COPE environments prioritize the separation of work and personal data, but the Keychain merging while switching Apple IDs on iOS devices undermines this separation. This has to be considered in situations where employees use their personal Apple IDs alongside corporate profiles on the same device. If one Apple ID during the Apple ID switching process is the corporate ID and the other is the private ID, that leads to merging of corporate and personal credentials compromising the security posture of COPE mobile environments and/or the privacy of the user’s private credentials.

Data retention dialogue when signing out from one Apple ID: When the “Keychain” option is selected in the dialogue whilst signing out from corporate Apple ID and before signing in to the personal Apple ID, stored corporate passwords are merged with stored personal passwords.
Corporate passwords from signed out corporate Apple ID are merged to saved passwords of personal Apple ID. All shown passwords are available in personal Apple ID.

Lack of Mitigation Through MDM Restrictions

Currently, there is an absence of Mobile Device Management restrictions to mitigate the unintended consequences of password merging during Apple ID switching. The inability to prevent Keychain merging in COPE environments can have a significant impact for organizations. The only measure is to enforce employee education and awareness regarding the risks associated with Apple ID switching and Keychain merging. Training programs should emphasize the importance of choosing secure options during account transitions and the potential impact on corporate and private data security.

Conclusion

The merging of Keychain entries during Apple ID switching on iOS devices poses a significant security challenge, particularly in COPE mobile environments. Organizations currently need to be proactive in addressing this issue through employee education and awareness programs. Collaboration between organizations, MDM providers and Apple, is needed to develop comprehensive solutions that safeguard corporate credentials and mitigate the risks associated with Apple ID switching.

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No Patch, no Trust: Consequences of iOS Data Flow Restriction Bypasses for Enterprises

The number of ways to bypass iOS data flow restrictions meanwhile has further increased, but Apple still does not bother to fix them. So, the question is: How trustworthy are iOS MDM restrictions if even simple tricks to bypass them are not closed by Apple?

In many enterprises, there is the need to separate data of different origins or trust levels. In COPE (company owned, personally enabled) deployments this typically is the separation between private and business apps. Whereas in COBO (company owned, business only) deployments often data of supporting tools (such as travel management) should be separated from confidential enterprise data or other data with higher protection requirements.

Apple acknowledges this demand of controlling the data flow, “to keep it protected from both attacks and user missteps” by applying the Mobile Device Management (MDM) settings “Managed Open In” and “Managed pasteboard”. However, we have already demonstrated that it is possible to circumvent these MDM restrictions with the pre-installed iOS Shortcuts App. Others also reported issues already in 2020 with the possibility to use the “Quick Look” functionality of the native iOS email client for a bypass, also demonstrated in a video.

New Findings

The recently new discovered and reported issues are related to the iOS Files app. The first issue is related to the “Recents” Tab of the Files app. When a user had opened any document in a managed app before and now open an unmanaged document in the “Recents” tab of the Files app, the share action incorrectly presents a list of managed apps instead of unmanaged apps. The opposite direction for the bypass (managed to unmanaged app) is the second newly reported issue. Deleting a managed document with the Files app and copying it to an unmanaged app folder (instead of restoring it) removes the MDM restriction and permits the user to open the document in the unmanaged app. This is also shown in our extended demonstration video, now demonstrating five unfixed issues with the iOS data flow restrictions.

Reactions to Reported Issues

We again reported the two new issues to Apple, but also this time, Apple argued that “MDM profiles provide configuration management but do not establish additional security boundaries beyond what iOS and iPadOS have to offer.” A similar argument was also given for the reported MDM restriction bypass of SySS GmbH.

For all these six bypass issues, there are currently no mitigations available. Taking all the current conversations with Apple into account, and as reported issues of 2020 are still not fixed, there seems to be no justifiable reason to believe that our findings will be fixed sooner.

Consequences for Enterprises

MDM restrictions are a vital instrument for securing the usage of iOS devices in enterprise environments. Only thanks to these restrictions, the requirements of enterprises can be fulfilled for a device that is primarily developed for the consumer market. Even with effective MDM restrictions it is still a challenging task for enterprises to keep up with constantly changed and extended features of mobile smartphone operating systems. And often enough, MDM restrictions that would make new features acceptable for enterprises are released only major versions later, if any (e.g., still no possibility to prevent a mix-up of private and enterprise passwords when switching between private and enterprise Apple IDs in COPE deployments, discussed in an upcoming article).

Experiencing the lack of support for fixing multiple reported issues in advertised security features now raises the question: Which other MDM restrictions are insecure? When one follows Apple’s argument, for any other bypass of such MDM restrictions a patch will be rejected and probably already have been rejected before, as MDM restrictions are always just configuration options per definition. This isn’t then only a technical issue, it becomes an issue of trust in supporting enterprises with reliable solutions.

In consequence, the missing patches reduce the possibilities for a secure iOS enterprise deployment in COPE and COBO scenarios.

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Trivial Bypass of iOS MDM Restrictions Apple doesn’t fix

Apple promotes MDM restrictions that should prevent data flows between managed and unmanaged apps. These restrictions can be bypassed easily and effortlessly using an app that is pre-installed on every new iOS device: the Shortcuts App. This is a finding of our practical tests on iOS 17.1 that should concern all enterprises that rely on these restrictions to use iOS devices in a compliant way with their enterprise policy for personal enabled usage.

Update: Problem is not only related to iOS Shortcuts App. MDM Restrictions can also be bypass with iOS Files App and iOS E-Mail client.

Apple promotes the data flow control between managed and unmanaged apps as a solution for data separation between personal and corporate data, “to keep it protected from both attacks and user missteps“. To achieve this protection, many enterprises configure the following Mobile Device Management (MDM) restrictions for the managed iOS devices:

Managed pasteboard. In iOS 15 and iPadOS 15 or later, this restriction helps control the pasting of content between managed and unmanaged destinations. When the restrictions above are enforced, pasting of content is designed to respect the Managed Open In boundary between third-party or Apple apps like Calendar, Files, Mail, and Notes. And with this restriction, apps can’t request items from the pasteboard when the content crosses the managed boundary.

Allow documents from managed sources in unmanaged destinations. Enforcing this restriction helps prevent an organization’s managed sources and accounts from opening documents in a user’s personal destinations. This restriction could prevent a confidential email attachment in your organization’s managed mail account from being opened in any of the user’s personal apps.

(see Apple Document “Managing Devices and Corporate Data”, accessed October 9th, 2023)

With the first restriction, a user should not be able to paste the content of the pasteboard to an unmanaged app, if the content was copied from a managed app, or vice versa. The second restriction applies the same restriction to documents. And in our tests, iOS prevented us from performing such actions, after the MDM restrictions for the test devices have been activated.

However, the iOS Shortcuts App, which is an integral part since iOS 13 and can be used to automate almost any task on iOS, can be abused to bypass such restrictions. The first shortcut (below on the left side) simply reads the clipboard and copies the content back to the global clipboard, which is then also synced with all other devices that the user has logged in with the same Apple account. When the user activates this shortcut, it strips of the information, that the original content was copied from a managed app and so iOS does no longer prevent the paste action to an unmanaged app. Each shortcut can also be combined with a trigger action that can automated the execution of it. So, the bypass of iOS MDM Restrictions can also be automated.

The second example shortcut uses the input of the share sheet to save the content of a document from a managed app. When using this shortcut in the share sheet, iOS prompts for name and location of the file and stores it without the information, that the content originated from a managed app. This way the document can be opened also from unmanaged apps. We created a video for both bypass methods to show the environment and the results in action. But these are only simple examples of the problem. There are many more possibilities to use actions of the Shortcuts App to bypass the iOS MDM restrictions.

Apparently, the Shortcuts App has privileges to access any data from managed apps, although it is not configured as a managed app through the MDM profile. This way the app can access the data, but when the data is saved by the Shortcuts App, it is saved as an unmanaged app. The fix therefore should be to keep the origin information of the content the Shortcuts app processes. This way the app could still access content from managed apps, but the processed content would be marked as originated from a managed app and this way the data separation would be kept intact.

We reported this flaw via Apple’s responsible disclosure process. However, the issue was rejected. We provided a detailed description, screenshots and videos, but also on a second try, where we explained again that the bypass circumvents an advertised security feature of iOS, it was not accepted. We also reached out to Apple via feedbackassistant.apple.com, but did not receive any answer in 2 months. As the current Shortcuts App version 6.1.2 is still vulnerable, we decided to publish the findings to warn enterprises that they cannot rely on iOS data flow restrictions.

A short-term solution would be to delete the iOS Shortcuts App from the devices and block the installation with the MDM blacklist via the bundle ID “com.apple.shortcuts” or to exclude devices with installed Shortcuts App from the domain as non-compliant, depending on the provided functionality of the MDM solution used. However, in the VMware Workspace ONE UEM (AirWatch) MDM tested, the Shortcuts App blacklisting did not prevent the installation nor was the device marked as non-compliant.

Without a proper blocking of the Shortcuts App, company data can currently be sent unintentionally in unmanaged apps through manually used or automated shortcuts and thus leave the company in an uncontrolled manner.

You can visit us on it-sa Expo&Congress, 10. – 12. October in Hall 6, Booth 210 for further details.

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Insecure Cryptography Usage: Tracing Cryptographic Agility in Android and iOS Apps

How has cryptography quality of the top 2000 Android and iOS applications evolved over the past three years? We show an overview of used hashing functions and symmetric encryption algorithms now and then. The results indicate that the majority of apps still use insecure cryptography.

Cryptography algorithms are applicable in many use cases such as for example encryption, hashing, signing. Cryptography has been used since centuries, some cryptography algorithms have been proven to be easily breakable (under certain configurations or conditions) and should thus be avoided. It is not easy for a developer with little cryptographic background to choose secure algorithms and configurations from the plenitude of options. Cryptographic agility is the ability exchange (insecure) cryptography algorithms with secure ones in computer programs.

Analysis Environment & Apps

The analysis results are based on the Appicaptor analysis results of the top 2000 Android and iOS apps. Appicaptor analyzed the current versions of the top 2000 apps along with the three-year-old counterpart of the respective apps. The apps are grouped into top apps from the top 2000 list and business apps uploaded or requested by Appicaptor customers.

Used Hashing Functions

Hashing functions such as MD5 and its predecessors as well as SHA1 are long known to be insecure and prone to collision attacks. It is advised by NIST to move to more secure alternatives like SHA224 or up to SHA512.

The used hashing functions in business apps and the top apps for iOS and Android were analyzed to see the current situation. Afterwards, the 2019 version of the apps is compared to the 2022 version to show the trend for cryptographic agility.

Percentage of apps using the specified hashing functions in top and business apps (2019 VS 2022)

Surprisingly, outdated SHA1 and MD5 hashing is still found in 70% to 80% of the analyzed apps and thus the most used hashing algorithms in iOS and Android in both, the top and business app groups. Even the long outdated MD2 algorithm is still used in 5% to 10% of all apps. These are alarming news regarding security. SHA256 is the only used, yet secure algorithm which is as widespread as MD5 and SHA1.

Comparing hashing in top and business apps, one can see that business apps use less hashing functionality in general.

Looking at the evolution of the top apps on Android and iOS from 2019 to 2022, one can see that the usage of MD5 and SHA1 mostly remains constant with only slight variations. On Android, the SHA2 family and especially SHA512 usage increased. In the case of SHA512, the usage in apps doubled, which is at first sight a positive trend. However, since the usage of outdated algorithms remains constant, one must say, that only more hashing algorithms are used and secure algorithms are not replacing the outdated ones. On iOS, the situation is vice versa: The usage of the SHA2 family even declines which leads to the assumption that less hashing is used on iOS.

In conclusion, one can say that even though Android developers embracing the SHA2 family, outdated hashing functions constantly and heavily remain in Android and iOS apps.

Used Symmetric Encryption Algorithms

As one would expect, AES is the most widely used symmetric encryption algorithm. DES and 3DES are used in around 3% of the analyzed apps. One exception is DES in Android which still seems very popular with a usage in around 12% of the tested apps. Throughout the years, DES and 3DES usage remains mostly constant. However, looking at AES usage over time, one can see that the usage in Android increases in the latest app versions, while at the same time the AES encryption in iOS decreases.
Especially on Android, a discrepancy between business and top apps becomes obvious. Business apps seem to use less AES and slightly more DES encryption.

Percentage of apps using the specified encryption functions in top and business apps (2019 VS 2022)

Usage AES in Insecure ECB Mode

Usage of the ECB mode is a very common weakness when applying cryptography. ECB mode outputs the same ciphertext for the same plaintext (when the same key is used). This means that pattern are not hidden very well and one could draw conclusions on the plaintext. With other techniques like CBC or CTR mode, succeeding block’s encryption depend on one another, which introduces randomness and hides pattern.
We are aware that under certain conditions the usage of ECB mode is fine, but we advise against using it since secure conditions might easily become insecure during app upgrades, code restructuring or new requirements.

We visualize the usage of insecure ECB mode versus other modes. In the visualization we lay focus on the explicit transition of used secure and insecure modes from 2019 to 2022.

ECB mode usage transitions from 2019 to 2022

Looking at the transitions for Android top apps, we see that 48.9% ECB mode usage in 2019 shrinks to 32.3% in 2022, which is very positive. One can also see that many apps shift from ECB mode to other secure modes. However, a small percentage of apps used secure cryptography in 2019, are now using ECB in 2022.

The situation on iOS looks much different. The transition diagram shows that out of the top apps on iOS, only 12% use ECB mode in 2019 and the majority uses secure alternatives. However, after three years, things didn’t turn out well for iOS apps. With 16% for top apps and 12% on business apps in 2022, more apps are using insecure ECB mode compared to 2019. Even though numbers increased on iOS, ECB usage on Android is still far more widespread, but decreases.

Causes of ECB mode usage

From all observations, we find the transitions from secure (non-ECB) to insecure (ECB) cryptography and vice versa very interesting. Understanding reasons for the transitions could give hints on how developers could be lead towards better cryptography standards. The transitions from ECB to non-ECB and non-ECB to ECB is significantly strong in Android top apps.

Triggers for a change from secure encryption (non-ECB) to insecure encryption (ECB) on Android and iOS

A more in-depth analysis of these apps reveals that in around 90% of the cases, the transition from ECB or towards ECB is triggered by an included third-party library. On iOS in 70% of the cases the transition is triggered through third-party libraries and in 30% of the cases through code changes of the app developer.

Libraries triggering transition insecure cryptography (non-ECB) to secure cryptography (ECB) on Android
Libraries triggering transition insecure cryptography (ECB) to secure cryptography (non-ECB) on
Android
ECB removal comes from library update or library removal from app

Different Android third-party libraries which cause the transition from an insecure to a secure cryptography mode and vice versa were analyzed. The transition from ECB to non-ECB is pretty clear, 98% of the apps discontinued using ECB due to not using Google GMS Advertisement library anymore. In 2% of the apps, the respective library was not identifiable due to obfuscation. The pie charts also show which libraries triggered the ECB usage in 2022 apps. Leading with 29% is Google GMS Advertisement library followed by Icelink (12%), Microsoft Identity (10%) and Apache Commons (10%). Respective apps were deeper analyzed, to see if ECB was introduced through a third-party library update or just by adding a new third-party library with ECB usage. In fact, in 92% of the cases libraries with ECB usage were added and only in 8% of the cases a third-party library update introduced ECB.

Conclusion

This analysis has proven that the majority of apps still use insecure cryptography. The trend over the past years unfortunately shows no significant drift towards secure algorithms on the broad front. Some single aspects like ECB usage on Android point into the right direction. The detailed analysis in finding causes of the ECB usage on Android showed that this flaw is mostly introduced through the usage of third-party libraries during app development.

Sources

The contents of this blog post is a condensed version of the award-winning paper published at the international ICISSP 2023 Conference. The full paper can be viewed at Scitepress.

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Content Security Policy – Important Defense-in-Depth missing for many Apps

The Content Security Policy (CSP) defines restrictions for webviews to reduce the attack surface of applications for Cross Site Scripting (XSS) and other attacks. The stricter the policy is configured, the fewer possibilities remain for attackers to inject malicious functionality in case of input validation flaws. This is especially important for hybrid apps, such those build with Cordova, that use JavaScript to access granted OS functionality via a JavaScript bridge. If an attacker can inject own code to a hybrid app’s webview, he can alter the way how the app uses accessible data and sensors.

A strict CSP can prevent the execution of injected functionality by restricting the executable code fragments to resources that are less accessible to an attacker. However, strict restrictions also require alternative programming styles during app development, which sometimes are inconvenient or unknown to the developer. Additionally, some external libraries or other existing code may not work out of the box with restrictive CSP settings, increasing the pressure for using a less restrictive policy.

With Appicaptor we inspect apps for configured CSPs to evaluate the restrictions for the security of the app. A single missing sanitation of user input may render a hybrid app vulnerable for hijacking of the app’s functionality in a malicious way. As the vulnerabilities can be introduced to apps by a missing ‘S’ for the HTTPS scheme when loading external JavaScript resources or by a flawed sanitation of user input, hybrid apps should reduce these risks by applying a ready to use second line of defense using CSPs. However, 60.5% of the analyzed hybrid apps for iOS and 72.3% of the hybrid apps for Android do not define a CSP. The analyzed app set each consists of the most used 2,000 apps as ranked by the Android and iOS App Stores.

One might consider a ratio of more than 25% for hybrid apps that do use CSP as a second line of defense an already good starting point. However, analyzing the actual CSPs of these apps shows that many policies are weak. In iOS 39.5% (Android: 27.6%) of the hybrid apps with a CSP deactivate important protective restrictions and therefore could be rated equally to apps with no defined CSP from the perspective of an attacker. So let’s see why.

This is a typical basic example of an observed CSP: 

<meta http-equiv="Content-Security-Policy" content="default-src 'self' data: 'unsafe-inline'; img-src *;">

CSPs are constructed in a simple fashion: Each section starts with the source keyword the directive should be applied to and is terminated with a semicolon. In the example the CSP starts a directive section with the default-src keyword. Its declared restrictions are used as fallback for other, not defined directives. For example, the directive for script-src and object-src are not declared, so the configuration of 'unsafe-inline' is applied to both of them, but not to 'img-src', as it is declared in the example and therefore the fallback to 'default-src' is not applied by the browser.

The intention here is to allow loading sources only from 'self', which is the source where the HTML page with the CSP entry was loaded from, to prevent injection of external scripts for Cross Site Scripting. Only images are allowed to be loaded from any source, declared by star character in the img-src directive.

However, by declaring the keyword 'unsafe-inline', this CSP allows executing JavaScript code injected at any place in an HTML page, such as

User entered <script>doSomethingBad();</script> text

or

<div onclick="doSomethingBad();">Click Me</div>

Allowing 'unsafe-inline' together with the data: scheme for the object-src in the example allows an attacker to inject script code to <object>, <embed>, and <applet> elements: 

<object data="data:text/html,<script>doSomethingBad();</script>"></object>

or by using JavaScript inside an SVG, embed as data: URL:

<embed src="data:image/svg+xml,<svg onload='doSomethingBad();' xmlns='http://www.w3.org/2000/svg'></svg>" type="image/svg+xml" width="1" height="1" />

Fortunately, in most common cases the code injected via data: scheme is treated as a separate frame. It cannot interact with the JavaScript bridge of a hybrid app, which is located in the parent index.html page and the Same Origin Policy prevents the access to it. However, attackers can still use this for UI manipulation attacks by tricking users to disclose credentials or other critical data in crafted dialogs.

Besides many other possible shortcomings observed CSP are having regarding inline XSS protection, about 10% of the analyzed hybrid apps (iOS / Android) do not properly restrict the sources for loading scripts. This is caused by using the star character as a wildcard for the scheme. This way an attacker would be able to inject a script element that can load malicious code from any domain. The same applies if instead the scheme https: is used. It seems that this configuration option is too confusing for developers as for some it might look like as if this configuration would just prevent HTTP access. However, if used it allows access to any domain via HTTPS. So, when some developers use the https: together with a list of domain names they want to allow, this domain list does not have any effect, as any domains are already allowed: 

default-src 'self' data: https: ssl.gstatic.com maps.google.com;

Such ineffective domain restrictions were observed in about 7% (iOS / Android) of the analyzed hybrid apps, which might give a false sense of security. Instead, the developer would need to specify the protocol together with the scheme (e.g. https://ssl.gstatic.com) to restrict access to listed domains and allow this access only via HTTPS.

Unfortunatly, in about 5% (iOS / Android) of the analyzed hybrid apps also parsing errors were detected that can prevent the intended protection. In general, such parsing errors could lead to more strict or less strict restrictions, depending on which part of the CSP is affected. However, as more strict policies that are accidentally created are more likely to cause functional issues than in the case of accidentally created less strict policies, the chance is much higher that those issues are detected in functional testing. For example, we observed parsing errors that prevent some or all directives from being applied. In all these cases, the errors lead to a less strict CSP, e.g. by omitting a good strict default-src directive that is now missing for a secure fallback for other non-specified directives.

CSPs can have a strong impact on app security. They are especially important for hybrid apps. The analysis results show that it is important to check if apps do use a CSP and that the CSP needs to be evaluated carefully. In case of doubt, developers should check the CSP with a free tool such as the Google CSP Evaluator to better understand the impact of the directives and to prevent parsing flaws.