I found a security breach in instawallet last week... I fixed it for them... they never tipped me or anything...
Correction: You found a "mistake" in their website. Some might call it a flaw, but it is certainly not a security flaw or exploit.
Please don't spread alot of FUD, this might actually be a serious matter. Someone might have exploited a real security vulnerability.
If you don't think that somebody just Googling up your Instawallet URLs along with your BTC in them, then you need to stop hiding your head in a hole.