Jonas Sicking discovered that under some circumstances persisted XUL attributes are associated with the wrong URL. A malicious web site could exploit this to execute arbitrary code with the privileges of the user. (MFSA 2006-35, CVE-2006-2775)
Paul Nickerson discovered that content-defined setters on an object prototype were getting called by privileged UI code. It was demonstrated that this could be exploited to run arbitrary web script with full user privileges (MFSA 2006-37, CVE-2006-2776).
The Mozilla developer team discovered several bugs that lead to crashes with memory corruption. These might be exploitable by malicious web sites to execute arbitrary code with the privileges of the user. (MFSA 2006-32, CVE-2006-2779, CVE-2006-2780)
Masatoshi Kimura discovered a memory corruption (double-free) when processing a large VCard with invalid base64 characters in it. By sending a maliciously crafted set of VCards to a user, this could potentially be exploited to execute arbitrary code with the user’s privileges. (MFSA 2006-40, CVE-2006-2781)
Kazuho Oku discovered various ways to perform HTTP response smuggling when used with certain proxy servers. Due to different interpretation of nonstandard HTTP headers in Thunderbird and the proxy server, a malicious HTML email can exploit this to send back two responses to one request. The second response could be used to steal login cookies or other sensitive data from another opened web site. (MFSA 2006-33, CVE-2006-2786)
The “enigmail” plugin has been updated to work with the new Thunderbird version.