How to get your browser DB off the device

Launch Firefox.
Open Settings.
Scroll down to "Version" and tap it several times.
Scroll down and hit "Debug: copy databases to app container".
Connect your device via USB.
Open Xcode.
Window > Devices. Choose your device.
Find "Firefox" on the right side.
Click the gear icon, and choose "Download Container…". Save it somewhere.
After some time, Finder will open focused on an .xcappdata file.
Right-click, "Show Package Contents".
Navigate to AppData/Documents. Zip up browser.*.