Mozilla Thunderbird is a standalone mail and newsgroup client. A use-after-free flaw was found in the way Thunderbird removed nsDOMAttribute child nodes. In certain circumstances, due to the premature notification of AttributeChildRemoved, a malicious script could possibly use this flaw to cause Thunderbird to crash or, potentially, execute arbitrary code with the privileges of the user running Thunderbird. Several flaws were found in the processing of malformed content. An HTML mail message containing malicious content could cause Thunderbird to crash or, potentially, execute arbitrary code with the privileges of the user running Thunderbird. A flaw was found in the way Thunderbird parsed certain Scalable Vector Graphics image files that contained eXtensible Style Sheet Language Transformations . An HTML mail message containing a malicious SVG image file could cause Thunderbird to crash or, potentially, execute arbitrary code with the privileges of the user running Thunderbird. A malicious script could possibly use this flaw to gain access to sensitive information that may be included in HTTP proxy error replies, generated in response to invalid URLs using square brackets. Note: The CVE-2011-3659 and CVE-2011-3670 issues cannot be exploited by a specially-crafted HTML mail message as JavaScript is disabled by default for mail messages. It could be exploited another way in Thunderbird, for example, when viewing the full remote content of an RSS feed. For technical details regarding these flaws, refer to the Mozilla security advisories for Thunderbird 3.1.18. You can find a link to the Mozilla advisories in the References section of this erratum. All Thunderbird users should upgrade to these updated packages, which contain Thunderbird version 3.1.18, which corrects these issues. After installing the update, Thunderbird must be restarted for the changes to take effect.