User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101 Firefox/68.0
Steps to reproduce:
Signed into Firefox account, then disconnected Sync.
It was turned on automatically and I didn't want to use the feature.
For more see:
It had already begun syncing data. When I disconnected Sync there was no option to delete data Sync stores on its server
Add an option to the "Disconnect Sync" modal that says something like:
 Delete all Firefox Sync data from my account