Google security researcher Michal Zalewski reported that when a malformed GIF image is repeatedly rendered within a <canvas> element, memory may not always be properly initialized. The resulting series of images then uses this uninitialized memory during rendering, allowing data to potentially leak to web content. External Reference: http://www.mozilla.org/security/announce/2014/mfsa2014-78.html Acknowledgements: Red Hat would like to thank the Mozilla project for reporting this issue. Upstream acknowledges Michal Zalewski 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.