By pure coincidence I found a spam post. This was a response to one of my comments and someone edited my quoted text in that response to add a URL which is definitely looking like a malware site (I did not check it out for security reasons).
It looks to me that the account that originally created the response got hacked - I tried to find any point in contact for the site administrators but did not see anywhere a chance to “contact support” or “flag as inappropriate” or whatever.
What can we do to report this kind of a problem?