Advanced Mac Cleaner popup?
Note: With Advanced Mac Cleaner malware, after the first scan, immediately restart and do a second scan to stop AMC from rewriting files.
1. Use MalwareBytes for Mac to remove malware/adware.
Install guide: https://support.malwarebytes.com/docs/DOC-1817
Uninstall Guide: https://support.malwarebytes.com/docs/DOC-1190
The installer may ask you to allow it in Security & Privacy /System Preference. Allow it.
2. Disable all extensions and test.
Turnoff or uninstall extensions.
Section: Manage extensions: https://support.apple.com/guide/safari/use-safari-extensions-sfri32508/mac
3. Choose a search engine.
Delete all text in the Smart Search field, click the magnifying glass , then choose a search engine from the list.
4. Set your Home Page. https://support.apple.com/guide/safari/set-your-homepage-ibrw1020/mac
5. Restart your Mac.
6. Launch Safari holding the Shift key down.