Mozilla developer Mark Hammond reported a flaw in how WebChannel.jsm handles message traffic. He found that when a trusted page is hosted within an <iframe> on an untrusted third-party untrusted framing page, the untrusted page could intercept webchannel responses meant for the trusted page, bypassing origin restrictions. 


External Reference:

http://www.mozilla.org/security/announce/2015/mfsa2015-56.html


Acknowledgements:

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

Statement:

This issue does not affect the version of firefox and thunderbird as shipped with Red Hat Enterprise Linux 5, 6 and 7.