Impact
If a user is instructed to open an image in a new tab (right click -> open in new tab, or copy the URL and paste it in the URL bar), an the image payload is executed on the domain hosting the app (app.wire.com).
In particular, if an image contains malicious code in addition to the actual picture, this code is executed on app.wire.com.
This allows the attacker to fully control the user account.
Patches
Before sending blob objects to URL.createObjectURL, we inspect their MIME type. Only image MIME types will be forwarded which prevents objects of MIME type "text/html" to execute JavaScript code.
Workarounds
Users should not try to open image URLs.
References
Credits
Reported by Kane Gamble.
Impact
If a user is instructed to open an image in a new tab (right click -> open in new tab, or copy the URL and paste it in the URL bar), an the image payload is executed on the domain hosting the app (app.wire.com).
In particular, if an image contains malicious code in addition to the actual picture, this code is executed on app.wire.com.
This allows the attacker to fully control the user account.
Patches
Before sending blob objects to URL.createObjectURL, we inspect their MIME type. Only image MIME types will be forwarded which prevents objects of MIME type "text/html" to execute JavaScript code.
Workarounds
Users should not try to open image URLs.
References
Credits
Reported by Kane Gamble.