[OT] Spyware Security Problems

Alrighty everyone,

I've been curious, as prevalent as it seems that spyware (and adware) seem to be on the internet, have there ever been any instances of hackers exploiting a hole in the offensive program in order to take control of the end users computer?

Is this possible? Has it happened? If so, can you provide a link to a description of the incident?

Thanks!