Security researcher Nils used the Address Sanitizer tool to discover two type confusion flaws. The first of these occurs while setting specific attributes of a source element resulting in incorrect object casting. The second flaw occurs when binding a source to a tree when the function fails to validate the namespace. These flaws lead to use-after-free errors, resulting in potentially exploitable crashes. External Reference: http://www.mozilla.org/security/announce/2015/mfsa2015-39.html Acknowledgements: Red Hat would like to thank the Mozilla project for reporting this issue. Upstream acknowledges Nils 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.