This indidates a possible attempt to exploit a buffer overflow vulnerability in IrfanView.
A remote attacker could execute arbitrary code on a victim system via a specially-crafted ".IFF" image file, if the attacker can persuade the victim to open a malicious file.
IrfanView PlugIns version 4.00 and prior.
System compromise: remote code execution.
Upgrade to IrfanView Formats PlugIn version 4.01 :