Mozilla developers David Chan and Gijs Kruitbosch reported that it is possible to create a drag and drop event in web content which mimics the behavior of a chrome customization event. This can occur when a user is customizing a page or panel. This results in a limited ability to move UI icons within the visible window but does not otherwise affect customization or window content.
Red Hat would like to thank the Mozilla project for reporting this issue. Upstream acknowledges David Chan and Gijs Kruitbosch as the original reporter.
This issue does not affect the version of thunderbird as shipped with Red Hat Enterprise Linux 5 and 6, or the version of firefox as shipped with Red Hat Enterprise Linux 5, 6, and 7.