That's a patch to protect against files carrying malicious code. If you read the summary, you'll see it says
Quote:
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A malicious BMP, DIB, RLE, or PNG must be opened in Photoshop or Photoshop Elements by the user for an attacker to exploit these potential vulnerabilities.
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For one of these exploits to work, the affected file (not just a PNG, but possibly one of the other filetypes listed) must be opened in Photoshop. The OP's problem is that Photoshop
won't open PNGs.