Security researchers Tim Philipp Schäfers and Sebastian Neef, the team of Internetwache.org, reported a mechanism using JavaScript onbeforeunload events with page navigation to prevent users from closing a malicious page's tab and causing the browser to become unresponsive. This allows for a denial of service (DOS) attack due to resource consumption and blocks the ability of users to exit the application. 


External Reference:

http://www.mozilla.org/security/announce/2014/mfsa2014-20.html


Acknowledgements:

Red Hat would like to thank the Mozilla project for reporting this issue. Upstream acknowledges Tim Philipp Schäfers and Sebastian Neef 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