Security researcher Mariusz Mlynski reported, through HP Zero Day Initiative's Pwn2Own contest, that documents loaded though a resource: URL, such as Mozilla's PDF.js PDF file viewer, were able to subsequently load privileged chrome pages. The privilege restrictions on resource: URLs was handled incorrectly and these restrictions could be bypassed If this flaw was combined with a separate vulnerability allowing for same-origin policy violation, it could be used to run arbitrary code.

In general this flaw cannot be exploited through email in the Thunderbird product because scripting is disabled, but is potentially a risk in browser or browser-like contexts.


External Reference:

http://www.mozilla.org/security/announce/2015/mfsa2015-33.html


Acknowledgements:

Red Hat would like to thank the Mozilla project for reporting this issue. Upstream acknowledges Mariusz Mlynski as the original reporter.