Need to block a user on github.

Hi,
Is it possible to you to block a user on github ?
I see this should be possible but I didn't see the button in github UI, so I guess I didn't have the right to do that.

This is about blocking user @slurfer71 which constantly send ads on a Wakaama issue. See discussion from here : https://github.com/eclipse/wakaama/issues/482#issuecomment-1169707548

Anyway idea how to resolve this ? or maybe I should report content to github ?