It appears some 'group' by the name of 'dengesiz' hacked my website. I've spent a good while going over everything and it appears that they didn't touch the database and only edited one file - '/language/english.php.'

I was speaking the 'language' of their group, which happened to involve a strange looking penguin in war dress and an insult to the Greek from the Turkish, which is presumably their nationality. The artwork was poor, but if you really want to see it the http logs showed they logged the hack at zone-h.org

As dangerous an assumption as it is, I am going to assume that they only compromised the single file, and keep everything else as-is. That is certainly the impression I get and I have been through everything. The question now is how to stop it happening again, and unfortunately all I can do is upgrade everything. (The logs and the hack don't have any match - I can't identify the http request that did it, so I can't trace the dam thing.)