This isn't a matter of transparency, was the OP legally bound not to disclose the RCE? That whole "embargo" was pure courtesy between the people involved. The OP committed no fault at first place and the exploit was already in the wild anyway. Whoever really wanted to exploit it before the patch could without using the OP as a source.

> Anyone can sue anyone else for any reason.

And it's easier to have cause to sue when someone publish an "admission of guilt", which makes a lawsuit harder to dismiss thus costlier.