Hmm, I still think extensions are the first place to look: You can view, disable, and often remove unwanted or unknown extensions on the '''Add-ons page'''. Either: * Command+Shift+a (Windows: Ctrl+Shift+a) * "3-bar" menu button (or Tools menu) > Add-ons * type or paste '''about:addons''' in the address bar and press Enter/Return In the left column of the Add-ons page, click Extensions. Then cast a critical eye over the list on the right side. Any extensions Firefox installs for built-in features are hidden from this page, so everything listed here is your choice (and your responsibility) to manage. Anything that is related to search, or which looks suspicious, or that you just do not remember installing or why? If in doubt, disable (or remove). Assume guilty until proven innocent. Any improvement? '''Update Settings''' Are you able to update your home page and default search engine on the Preferences page: * [[How to set the home page]] * [[Change your default search settings in Firefox]] If those cannot be changed, or if they revert back, please let me have a little more detail. For example, won't accept a change at all, or change is reverted at the next startup, etc. If relevant: [[How to fix preferences that won't save]] '''Malware Scan''' This is the only program I know for Mac: https://www.malwarebytes.com/mac/ Hopefully it can strip out problem software that may be modifying Firefox settings.