If you have some time to spare, could you test whether the upstream builds (which can be downloaded from https://www.mozilla.org/firefox/download/thanks) are similarly affected, and if so, file an upstream bug report at https://bugzilla.mozilla.org/enter_bug.cgi#h=dupes%7CFirefox ?
** Changed in: firefox (Ubuntu) Status: Incomplete => New -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1898656 Title: Firefox not playing YouTube videos in Virtualbox on Xubuntu To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/firefox/+bug/1898656/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs