USN-978-1 fixed vulnerabilities in Thunderbird. Some users reported stability problems under certain circumstances. This update fixes the problem. We apologize for the inconvenience. Original advisory details: Several dangling pointer vulnerabilities were discovered in Thunderbird. An attacker could exploit this to crash Thunderbird or possibly run arbitrary code as the user invoking the program. It was discovered that the XPCSafeJSObjectWrapper security wrapper did not always honor the same-origin policy. If JavaScript was enabled, an attacker could exploit this to run untrusted JavaScript from other domains. Matt Haggard discovered that Thunderbird did not honor same-origin policy when processing the statusText property of an XMLHttpRequest object. If a user were tricked into viewing a malicious site, a remote attacker could use this to gather information about servers on internal private networks. Chris Rohlf discovered an integer overflow when Thunderbird processed the HTML frameset element. If a user were tricked into viewing a malicious site, a remote attacker could use this to crash Thunderbird or possibly run arbitrary code as the user invoking the program. Several issues were discovered in the browser engine. If a user were tricked into viewing a malicious site, a remote attacker could use this to crash Thunderbird or possibly run arbitrary code as the user invoking the program. David Huang and Collin Jackson discovered that the lt;objectgt; tag could override the charset of a framed HTML document in another origin. An attacker could utilize this to perform cross-site scripting attacks. Paul Stone discovered that with designMode enabled an HTML selection containing JavaScript could be copied and pasted into a document and have the JavaScript execute within the context of the site where the code was dropped. If JavaScript was enabled, an attacker could utilize this to perform cross-site scripting attacks. A buffer overflow was discovered in Thunderbird when processing text runs. If a user were tricked into viewing a malicious site, a remote attacker could use this to crash Thunderbird or possibly run arbitrary code as the user invoking the program. Peter Van der Beken, Jason Oster, Jesse Ruderman, Igor Bukanov, Jeff Walden, Gary Kwong and Olli Pettay discovered several flaws in the browser engine. If a user were tricked into viewing a malicious site, a remote attacker could use this to crash Thunderbird or possibly run arbitrary code as the user invoking the program