Cheerios: Sorry for Explicit Bee Sex Picture

The Cheerios honeybee got the XXX treatment on the front page of an official Cheerios website this morning -- thanks to some mischievous vandal -- and now, General Mills is scrambling to clean up the mess.

It's supposed to be a website for kids to make their own Cheerios-themed comics -- but clearly, someone got carried away ... and the explicit cartoon made it to the top of the popular "Honey Defender" website.

A rep for the cereal company tells TMZ, “We have some safeguards that are supposed to keep this from happening, but I guess it wasn’t set up with this game."

The rep adds, "Normally, our games where we allow viewers to spell out things themselves have safeguards that tell children they can’t type stuff like that in. Let’s just say this is no longer going to be the 'Hot Comic of the Week' much longer!”