Security fixes at https://www.mozilla.org/en-US/security/known-vulnerabilities/firefox/#firefox52, it also drops support for NPAPI plugins other than flash.
And there I was hoping flash would finally die.
What the release notes don't say is that they've made pulse a hard requirement for audio - I've got pics for youtube nad local mp4, ogv files - but no sound. Looks like https://bugzilla.mozilla.org/show_bug.cgi?id=1247056 : in theory, pulse is dlopened so it might be possible to add it after firefox. But we disable pulse in our mozconfig, and that was not flagged up as an invalid option.
I'll upload the latest version of the patch for system graphite2 and harfbuzz.