Sites images changed to spammy ones. Is my router hacked?

[parambyte]

I recently noticed my OSClass classifieds site thumbnails wer replaced by one single image of a strange provocative woman. (Ahem).

When I click on the thumbnail and seek image address, it points to the correct image on my server (not the woman image).

I also noticed posting something on stumbleupon and the posted thumbnail was different from the article's image.

I saw this happen in three different office computers, all password protected with limited root access, all connected to the same router, but haven't seen this happen in my home computer.

Could it be someone is injecting images via the router? How could I fix this?

[keyplyr]

That certainly could be the reason if all 3 machines connected to that router are affected, but not other machines.

Make sure to purge cache on all browsers (several times) to get accurate display.

I'd change router settings/password, then go through all site directories and check for affected files.