Firefox 25 works fine in our environment. Since the Firefox 26 update was made available, installing the update cleared the bookmarks in the bookmarks menu and the history from the history menu. When we rolled back to version 25, the bookmarks and the history appears again. The same behavior happens with Firefox 27. In addition to bookmarks and history disappearing, when Firefox 25 is update to version 26 but this is also true for versoin 27, it freezes up when accessing websites like Google.com, CNN.com, etc. No crash report logged in about:crashes each time this happens, the freezing of the browser also happens when running Firefox in Safe Mode so it has nothing to do with add-ons. Force Quit is the only option to get out of it and Activity monitor does not show Firefox using up too much CPU nor RAM, it just says (not responding). However, when we "reset Firefox", websites like Google and CNN no longer causes it to freeze. Even so, the bookmarks and history are still gone. But similarly, installing Firefox 25 over Firefox 27, puts back the bookmarks and history again. We have upgraded from lots of previous version of Firefox leading to Firefox 25, and never seen behavior like Firefox 26 and 27. I also noticed this happening on machines where the home directories are in NAS (network attached storage). This don't seem to happen in accounts with Libraries residing locally. I have monitored file changes of the Firefox 26 or 27 updates compared to the Firefox 25 installations via tools like Casper Suite Composer and FSEventer and the files affected are identical to me. Although I have not looked deeper into the contents of the files installed i.e. programming codes behind the update. I have read the release notes as well and nothing popped to me that will make Firefox 26 and 27 stop for LDAP accounts.