It's certainly possible. But I've only ever seen this on StackExchange sites. I have too many extensions (all mainstream) to want to test with them all disabled (especially as I can't repro it on demand) :/ And reloading the page gives the expected text ... next time it happens I will lokk at the page source and see if that gives any clues ...

Have you inspected the code? How is this added, maybe via some div; check its name or class then and tell there. Also, I don't seem to be able to find anything by goolgling the keywords appearing in your screenshots.

@nicael On my list next time is see the oddity ;)

So when you reload the page it's gone?

@nicael Yes, correct

Strange; Can you see multiple entries of this heck on one page, or only one per page?

Seems that the "news provider" differs each time; do they ever repeat?

@nicael Strange indeed. Only one per page so far, but I haven't checked thoroughly. I'm eagerly waiting for the next one so I can look at the page source.

Also, the news provider doesn't really look real.

Yes, one repeat so far which was "Random news" ... at the end of the summary. The last one is different and it completely replaced the summary.

Ghosts in the machine :)

Not real is one reason it is so strange.

I likw Anna's explanation so far until I figure out a better one " Yeah, my money is on the user pasting some text in to get past the quality filter and then attempting to ninja-edit until they found a magic combination of text that worked."

So far all posts are from new users who have just joined ...

This doesn't sound right in any case. Why would he ever bother finding & copying some random news; users mostly copy "This question doesn't meet our quality standards..." message, then edit it out.

(Also, just btw: the room id is 888; look at the top bar :)

Hmm. I don't a room ID :/

</offtopic>

The pasting spam by mistake is barely feasible...