Dynamically changing the style of an element from position:relative to position:static can cause Gecko to operate on freed memory. It may be possible to exploit this in order to run arbitrary code.
This flaw was introduced during Firefox 1.5 and SeaMonkey 1.0 development and does not affect Firefox 1.0 or the Mozilla Suite 1.7
Thunderbird 1.5 could be vulnerable if JavaScript is enabled in mail. This is not the default setting and we strongly discourage users from turning on JavaScript in mail. Thunderbird is not vulnerable in its default configuration.
Update (13 April 2006)
This flaw has been fixed in Thunderbird 1.5.0.2
Upgrade to the fixed versions. Do not enable JavaScript in Thunderbird or SeaMonkey mail.
Vulmon