As you mention Safari, you can rollback if you're on macOS using the steps below.
(If you're on iPhone or iPad, you're stuck on the latest version now. There isn't a way to rollback.)
Go to this site: https://ftp.mozilla.org/pub/firefox/releases/156.0.1/mac/
Go into the folder for the language version you want (e.g. en-US for American English)
Download the .DMG or .PKG file there (or maybe both)
Go into your Applications folder, and drag your current Firefox to the trash
Once it's gone, use the .DMG or .PKG to install the previous 156.0.1 release
After it's installed, go immediately to Menu -> Settings -> About Firefox and change the installation
option to "Check for updates, but choose when to install", or it'll update to 157.0 again in the background
You may also be able to recover bookmarks from the backups.
In the URL bar in Firefox, type about:profiles and then click the "Open Folder" buttons
In the Finder window that opens, look for a folder called "bookmarkbackups"
The files have the date they were created in the start of the filename (e.g. "bookmarks-2026-10-03_"_)
Find the most-recent one before you lost any, and copy it to another folder
Then go to Menu -> Bookmarks -> Manage bookmarks -> Import and Backup -> Restore -> Choose file
And then browse to and select the backup file you just copied
