Multiple security issues have been found in Icedove, Debian"s version of the Mozilla Thunderbird mail and news client. Multiple memory safety errors, use-after-free vulnerabilities, missing permission checks, incorrect memory handling and other implementaton errors may lead to the execution of arbitrary code, privilege escalation, information disclosure or cross-site request forgery. As already announced for Iceweasel: We"re changing the approach for security updates for Icedove in stable-security: Instead of backporting security fixes, we now provide releases based on the Extended Support Release branch. As such, this update introduces packages based on Thunderbird 17 and at some point in the future we will switch to the next ESR branch once ESR 17 has reached it"s end of life. Some Icedove extensions currently packaged in the Debian archive are not compatible with the new browser engine. An updated and compatible version of enigmail is included with this update. The icedove version in the oldstable distribution is no longer supported with full security updates. However, it should be noted that almost all security issues in Icedove stem from the included browser engine. These security problems only affect Icedove if scripting and HTML mails are enabled. If there are security issues specific to Icedove we"ll make an effort to backport such fixes to oldstable.