Are you running security software besides MS Defender?

Windows home or pro?

If you're running windows pro, you can also test in Windows Sandbox (VM) to see if you have the same issue. https://www.howtogeek.com/399290/how-to-use-windows-10s-new-sandbox-to-safely-test-apps/

Also try a different version of Firefox(Beta, Dev, or Nightly) and see if you have the same issue. Make sure to install in a different directory than your current install. https://www.mozilla.org/en-US/firefox/channel/desktop/ Make sure to install in a different directory from the current install.

You can also boot windows to safe mode with networking to see if you still have the same issue.

i only use MS Defender, and im on windows home, and i do have a windows VM from virtualbox where i tried it and it worked on there

tried the nightly build, which does work, i can copy something, but when i want to paste i have to press paste atleast a couple of times before it even pastes once

windows safe mode did not seem to work either

Interesting... Where did you get Firefox from? Also see what happens under a different windows user account. If you don't have one, create it or use admin.

i got firefox from the official firefox download site

and it does work under a new user

weird that it doesnt work on mine

i got firefox from the official firefox download site and it does work under a new user weird that it doesnt work on mine

So we now know it's not browser issue.