On July 15, cybersecurity firm Symantec revealed that attackers can manipulate users’ WhatsApp and Telegram media files on Android because of a ‘Media File Jacking’ flaw in the apps. It affects WhatsApp for Android by default, and Telegram for Android if certain features are enabled. “It stems from the lapse in time between when media files received through the apps are written to the disk, and when they are loaded in the apps’ chat user interface (UI) for users to consume,” Symantec said. How does this flaw work? WhatsApp, by default, saves received media files in external storage. On Android devices, files saved to external storage are “world-readable/writeable, so they can be modified by other apps or users beyond the app's control”, while files saved to internal storage can be accessed only by the app itself. Similarly, in Telegram, if a user enables ‘Save to Gallery’ feature, files will be saved in external storage. Consequently, when these files are saved to external storage, other apps with write-to-external storage permission can potentially manipulate these media files. Symantec found that nearly 50% of a given device’s apps have this permission. Here's what WhatsApp told MediaNama: “WhatsApp has looked closely at this issue and it’s similar to previous questions about mobile device storage impacting the app ecosystem. WhatsApp follows current best practices provided by operating systems for media storage and looks forward to providing updates in line with Android’s ongoing development. The suggested changes here could both create privacy complications for our users…
