Step .1
1. Click in the menu bar and choose “Force Quit”.
In the window that opens up, select “Safari” and click “Force Quit.
2. Relaunch Safari holding the shift key down.
This will launch Safari in Safe Mode.
The pop-up that crashed Safari will not return.
3. Turn off wifi and turn it back on.
Turn off Wifi. Click Wifi icon in the menu bar and select “Turn Wifi off”.
Visit another website.
You won’t have internet connection.
Turn on Wifi. Click Wifi icon in the menu bar and select “Turn Wifi on”.
Select your Network.
4. Delete Cookies
Safari > Preferences > Privacy > Cookies and other website data:
Click the “Manage website data” button.
Remove all cookies except ones from Apple, your internet service provider and banks.
If the step posted above doesn’t help:
Step 2
You will have to do this after starting up in Safe Mode to prevent adware
from interfering with the removal of adware .
1. Shut down the computer.
Press the power button. Immediately after you hear the startup sound,
press and hold the Shift key.
The Shift key should be pressed as soon as possible after startup,
but not before the startup sound.
Release the Shift key when you see the Apple logo on the screen.
Startup will take longer than usual.
Screen flickering is normal in Safe Mode.
Login to your account. Launch Safari.
Enter this address https://www.malwarebytes.org/antimalware/mac/
in the Safari address bar.
Download, Install , open, and run it by clicking “Scan” button to remove adware, if present.
Once done, quit MalwareBytes.
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.
https://support.apple.com/guide/safari/customize-your-search-ibrwe75c2a3c/mac
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.
Step.3
If steps 1 & 2 don't help, please run EtreCheck and post the report here if you can .
https://etrecheck.com
Click “Free Download” button, open Downloads folder, click on it to open, and then select ”Open”.
Click on the bouncing EtreCheck icon in the Dock.
“Choose a problem” from the popup menu box, and then “Start EtreCheck” in the dialog.
Click “Share Report” button in the toolbar, select “Copy to Clipboard” .
Paste it into the reply.