Firefox can't create new Issues

I recently updated my Firefox to 88.0 on Linux. Now I am not able to create any issues in my own repository. After hitting submit new Issue the following page shows up. It works on Chrome but I want to use Firefox. It also occurs in the safe mode of Firefox. The Firefox console tells me that the server sent this error:

HTTP/2 422 Unprocessable Entity 154ms

I now found the problem. The user session cookie expired but wasn’t deleted which is probably due to an add-on I use. However the github server doesn’t like to give a more precise error message. That isn’t in the client’s favor.

My question (now) is where can one give Github a feedback on their services?

:wave: Most of these issues are caused by extensions and add-ons - there’s no way to account for them all. In general if our suggested troubleshooting (disable extensions/try another browser) on the error page doesn’t help, contacting support is your next step.

I think this is the only support for website related questions. And the missing detail in the error message seems like a design flaw to me.
But I am investigating on github’s cookie behaviour since the add-on is quite useful.