User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:36.0) Gecko/20100101 Firefox/36.0 Build ID: 20141027113017 Steps to reproduce: Watch a video on Youtube with 460p, 1080p, 2k or 4k. Go full screen (maximize video). Exit full screen. Actual results: Crashes instantly or a few seconds later. After crash FF starts in full screen (F11) on the last used tab, even if you used another website without full screen after the video. Expected results: Not crash.
I'm not able to reproduce the crash with this YT video: https://www.youtube.com/watch?v=6v2L2UGZJAM Could you test with a clean profile, please. https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles In addition provide some crash IDs (bp-...) from about:crashes.
bp-9aff1e36-8371-45c5-af41-6a8352141027 bp-d3bd23b1-ef8e-4c33-97f2-e30c12141027 bp-2519f891-d56e-4153-8ad8-8a9fb2141028 I don't know. At the moment it doesn't crash. I'll have a look if it happens again on what exactly was different.
Don't forget to try on a clean profile