As part of the Firefox 1.5.0.2 release we fixed several crash bugs to improve the stability of the product, with a particular focus on finding crashes caused by DHTML. Some of these crashes showed evidence of memory corruption that we presume could be exploited to run arbitrary code with enough effort.
Thunderbird shares the browser engine with Firefox and could be vulnerable if JavaScript were to be enabled in mail. This is not the default setting and we strongly discourage users from running JavaScript in mail.
Upgrade to the fixed versions. Do not enable JavaScript in Thunderbird or the mail portion of SeaMonkey.
Also fixed in Firefox/Thunderbird 1.0.8, Mozilla Suite 1.7.13:
Fixed in Firefox 1.5.0.2, not applicable to older releases: