Red Hat Security Advisory 2015-1682-01 – Mozilla Thunderbird is a standalone mail and newsgroup client. Several flaws were found in the processing of malformed web content. A web page containing malicious content could cause Thunderbird to crash or, potentially, execute arbitrary code with the privileges of the user running Thunderbird. Note: All of the above issues cannot be exploited by a specially crafted HTML mail message because JavaScript is disabled by default for mail messages. However, they could be exploited in other ways in Thunderbird .