Bugzilla developer Frédéric Buclin reported that the X-Frame-Options header is ignored when server push is used in multi-part responses. This can lead to potential clickjacking on sites that use X-Frame-Options as a protection. External Reference: http://www.mozilla.org/security/announce/2013/mfsa2013-58.html Acknowledgements: Red Hat would like to thank the Mozilla project for reporting this issue. Upstream acknowledges Frédéric Buclin as the original reporter. Statement: This issue does not affect the version of firefox and thunderbird as shipped with Red Hat Enterprise Linux 5 and 6