I blocked Grammarly at my last company, nothing like giving a company tracking access to everything you type or read, and their EULA gives them the rights to everything they track.
Using Grammarly is stupid, paying them is downright insane.
We block extensions, period, on Google Chrome, as it prevents most malware outright. But then we've also discovered Grammarly's Microsoft Office plugin installs to the user folder (without requiring admin rights) as well. I've made a request to our antivirus vendor to add detection and blocking of Grammarly specifically, for the moment we're detecting it a different way.
That's OK, I figured he or she may not want to publicly reveal details, that is understandable in this case imho. As I said I was just curious if it was maybe a simple solution that could be implemented elsewhere.
Yes. Google offers ADMX templates for controlling Chrome which can be deployed through group policy. It includes an extension blacklist, which accepts wildcards. In my case, I put a * in there. It also has an extension whitelist, and a list of "force-installed apps and extensions".
I found a Firefox ADMX template project on GitHub, though it's third party and entails running a VBS file on system startup, so I wouldn't recommend it.
Using Grammarly is stupid, paying them is downright insane.