If you are using it and notice problems, it's best to log an issue or let us know at greasemonkey-dev (and be clear that it's with this version).
- The GM_info object now has a scriptSource property, like Tampermonkey. (#1738)
Greasemonkey is a Firefox extension that allows you to customize the way webpages look and function.
Hundreds of scripts are already available for free. And if you're the tinkerer sort, you can also write your own.