That's a toughie. Convert JPGs to PNGs and back?
I'm sorry, but that is a tad too creative :) I'd use a virus scanner like File::Scan or clamav and scan the files for viruses upon upload.

MJD says "you can't just make shit up and expect the computer to know what you mean, retardo!"
I run a Win32 PPM repository for perl 5.6.x and 5.8.x -- I take requests (README).
** The third rule of perl club is a statement of fact: pod is sexy.

In reply to Re^4: prevent arbitrary code execution in images by PodMaster
in thread prevent arbitrary code execution in images by bear0053

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