IF you really want to get scared about content theft, you should read the terms of service for Grammerly. Their plug in scans everything data input window and by using the service you agree to the following:
"By uploading or entering any User Content, you give Grammarly (and those it works with) a nonexclusive, worldwide, royalty-free and fully-paid, transferable and sublicensable, perpetual, and irrevocable license to copy, store and use your User Content (and, if you are an Authorized User, your Enterprise Subscriber’s User Content) in connection with the provision of the Software and the Services and to improve the algorithms underlying the Software and the Services."
If you were to write a book online using Grammerly they would have the full rights to what you wrote, and they could sell it themselves and not pay you a cent.
If you work for a company that uses Grammerly any IP typed into a windowd monitored by Grammerly also becomes their property.
Two years ago I looked into an enterprise license because I had so many employees using it, after reading the terms of service and speaking with their General Counsesl where he essentially gave the "my way or the highway speech","we own it all, and we can do what we want with it" I scrubbed the software and plugins from all our company computers.
Run from Grammerly