Security researcher Mitchell Harper used Valgrind to discover incorrect memory management for simple-type arrays in WebRTC. This waas undefined behavior which is theoretically dangerous but was determined to be safe in this instance. External Reference: http://www.mozilla.org/security/announce/2015/mfsa2015-36.html Acknowledgements: Red Hat would like to thank the Mozilla project for reporting this issue. Upstream acknowledges Mitchell Harper 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.