After this, one of my posts (hard deleted by a moderator, unfortunately...) had been replaced with a spam post about erectile disfunction. Unfortunately this post was removed before I could get a screenshot of it, but the actual post was displayed as a spam advert, but hiding the post and viewing it again showed its actual content (my real post). Editing the post also showed the real content, not the content on erectile dysfunction.
I have run a file health check on the installation from the ACP and I have checked for files on the server that arent supposed to be there. I have also run a virus scan on my own machine.