Issue Overview: On some systems–depending on the graphics settings and drivers–it was possible to force an out-of-bounds read and leak memory data into the images created on the canvas element. This vulnerability affects Firefox < 120, Firefox < 115.5, and Thunderbird < 115.5.0. (CVE-2023-6204) It was possible to cause the use of a MessagePort after it had already been freed, which could potentially have led to an exploitable crash. This vulnerability affects Firefox < 120, Firefox < 115.5, and Thunderbird < 115.5.0. (CVE-2023-6205) The black fade animation when exiting fullscreen is roughly the length of the anti-clickjacking delay on permission prompts. It was possible to use this fact to surprise users by luring them to click where the permission grant button would be about to appear. This vulnerability affects Firefox < 120, Firefox < 115.5, and Thunderbird < 115.5.0. (CVE-2023-6206) Ownership mismanagement led to a use-after-free in ReadableByteStreams This vulnerability affects Firefox < 120, Firefox < 115.5, and Thunderbird < 115.5.0. (CVE-2023-6207) When using X11, text selected by the page using the Selection API was erroneously copied into the primary selection, a temporary storage not unlike the clipboard. This bug only affects Thunderbird on X11. Other systems are unaffected. This vulnerability affects Firefox < 120, Firefox < 115.5, and Thunderbird < 115.5.0. (CVE-2023-6208) Relative URLs starting with three slashes were incorrectly parsed, and a…Read More