Security researcher Armin Razmdjou discovered that a man-in-the-middle (MITM) attacker spoofing a Mozilla sub-domain could bypass user approval messages to install a Firefox lightweight theme. This was possible because add-on installations of the lightweight themes do not require the use of HTTP over SSL. Firefox extensions were not directly affected and still required user approval for installation. External Reference: http://www.mozilla.org/security/announce/2015/mfsa2015-32.html Acknowledgements: Red Hat would like to thank the Mozilla project for reporting this issue. Upstream acknowledges Armin Razmdjou 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.