Please consider next time to turn on send info to Mozilla from within Firefox before posting. The information helps instead of guessing. Did not list what you tried. This would have been helpful. No idea so if not there yet please update to version 57.0.2 https://support.mozilla.org/en-US/kb/update-firefox-latest-version Since no info please try this : https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode If works fine in above then it is a installed Extension. Please disable all extensions and TEST and add back 1 at a time and TEST. Safe Mode does other things also so make sure test in it. Please uninstall Flash 21.0 r0 as 100's of Security Issues. Flash Player Version: 28.0.0.126 Current Version https://get.adobe.com/flashplayer/otherversions/ Step 1: Select Operating System Step 2: Select A Version (Firefox, . . . .) Note: Other software is offered in the download. <Windows Only> Please note that some sites use Flash Cookies and having a outdated Flash would then not allow cookies to be set within the Flash Applet in the Control Panel. If still issues : uninstall Firefox. Then Delete the Mozilla Firefox Folders in C:\Program Files and C:\Program Files(x86) Then restart system. Then run Windows Disk Cleanup. (Note: This should be Pinned and run Weekly, If never done below expect 10's of gig's) Then run it again and click the button that says Cleanup System Files. Note: your Firefox Profile is saved. But you should make a back up before you do : https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer Reinstall with Current Release Firefox 57.0.2 with a Full Version Installer https://www.mozilla.org/firefox/all/ Please let us know if this solved your issue or if need further assistance.