Hi, are you having this problem on an iPhone/iPad, or on a Mac? Either way, Yahoo is not provided by Mozilla, so more investigation is needed: ''For MacOS'' If the problem is Yahoo appearing at startup page, check your home page setting: [[How to set the home page]]. If the drop-down on the address bar indicates that search will go to Yahoo, check your default search engine setting to make sure it's still Google: [[Change your default search settings in Firefox]]. If the drop-down on the address bar indicates that search will go to Google, yet you end up getting results on Yahoo, that's likely due to an add-on or external program. 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 mentions search or privacy, or looks suspicious, or that you just do not remember installing or why? If in doubt, disable (or remove). Any improvement? For external malware, this is a well-regarded cleaner (free version and/or free trial): https://www.malwarebytes.com/mac/