Maybe your Firefox was infected by malwares: *[https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-caused-malware Problems caused by malwares] You can try do a clean reinstall: Certain Firefox problems can be solved by performing a ''Clean reinstall''. This means you remove Firefox program files and then reinstall Firefox. Please follow these steps: '''Note:''' You might want to print these steps or view them in another browser. #Download the latest Desktop version of Firefox from http://www.mozilla.org and save the setup file to your computer. #After the download finishes, close all Firefox windows (click Exit from the Firefox or File menu). #Delete the Firefox installation folder, which is located in one of these locations, by default: #*'''Windows:''' #**C:\Program Files\Mozilla Firefox #**C:\Program Files (x86)\Mozilla Firefox #*'''Mac:''' Delete Firefox from the Applications folder. #*'''Linux:''' If you installed Firefox with the distro-based package manager, you should use the same way to uninstall it - see [[Installing Firefox on Linux]]. If you downloaded and installed the binary package from the [http://www.mozilla.org/firefox#desktop Firefox download page], simply remove the folder ''firefox'' in your home directory. #Now, go ahead and reinstall Firefox: ##Double-click the downloaded installation file and go through the steps of the installation wizard. ##Once the wizard is finished, choose to directly open Firefox after clicking the Finish button. More information about reinstalling Firefox can be found [https://support.mozilla.org/en-US/kb/troubleshoot-and-diagnose-firefox-problems?esab=a&s=troubleshooting&r=3&as=s#w_5-reinstall-firefox here]. <b>WARNING:</b> Do not run Firefox's uninstaller or use a third party remover as part of this process, because that could permanently delete your Firefox data, including but not limited to, extensions, cache, cookies, bookmarks, personal settings and saved passwords. <u>These cannot be recovered unless they have been backed up to an external device!</u>

Ah, didn't realize I could just delete the program folder and re-install it. So far it seems to have fixed the problem. Now to figure out where the bug came from...

It can have infected your Firefox folder