to commonly asked questions.

Why is Firefox crashing?

Scotty I haven’t been able to log onto Firefox now for a coupla days,
I know you prefer
Safari but I have a lot of sites “bookmarked” on
Firefox that I’d like to access; what gives???

I haven't heard of any specific problems from other Firefox users lately so it may be a small issue. First things to try:

Step 1: First step troubleshooting any problem is to isolate whether the issue is related to your user or your Operating system. To do this, you can log into a different "test" or even "guest" user then try Firefox. If it works fine, it's not Firefox, it's your personal settings. Proceed to step 3. If you are experiencing the same issue in the guest user proceed to step 2.

Step 2: Delete Firefox from your applications folder then redownload it from (This will not get rid of your bookmarks). This will ensure you have the most up to date version.
If that doesn't take care of it, next step is to check the version of your MacOS. We are currently on 10.15.5 Catalina.

If that doesn't solve it move ahead. Warning (advanced and could lead to losing bookmarks)

Step 3: You can go to the "hidden" library by holding down the Option key while looking under the "Go" menu in the finder. Once in the hidden library folder, you can drag the following items into a folder on the desktop. Warning: this could remove bookmarks temporarily.

Preferences/com.mozilla… or com.firefox…
Application Support/ mozilla folder or firefox folder

Restarting Firefox will rebuild these files and may solve the issue. Then the issue of restoring bookmarks comes in.
This image is a theme.plist hack