@otto42:
In other words, if you ever got hacked before, and did not completely wipe your site clean and sanitize everything, then that’s probably how they got back in.
I keep seeing this, but considering that my site was a brand-new, fresh install of 2.5.1 in every way (new host, new server, etc.) and received the *exact same* hack – I don’t think it’s the issue you’re describing.
BUT, if somebody can create a user on your blog through some other method, then they can use the xmlrpc to make a post.
There were no new users added to my site – the first post was just hacked with:
<span style="overflow: hidden; position: absolute; height: 0pt; width: 0pt;"><a href="https://kvantservice.com/">компютри втора употреба</a></span>
And everything after the “more” tag was gone.