Mozilla Firefox before 3.6.18 and 4.x through 4.0.1, Thunderbird before 3.1.11, and SeaMonkey through 2.0.14 allow remote attackers to cause a denial of service (memory corruption and application crash) or possibly execute arbitrary code via a multipart/x-mixed-replace image.
If a malicious site uses the "view-source:" protocol in a series within a single hyperlink, it can trigger a non-exploitable browser crash when the hyperlink is selected. This was fixed by no longer making "view-source:" linkable. This vulnerability affects Firefox < 52 and Thunderbird < 52.