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Mac users are once again being urged to exercise caution when installing updates to Adobe Flash Player, after a fake update was discovered infecting computers.
Intego security experts have identified the rogue package installer as a variant of OSX/InstallCore, and have updated Intego VirusBarrier definitions to provide protection. [...]
The in-the-wild attack has been spread in the form of a Mac Package installer .pkg file, also known a flat package, and has been signed with a legitimate Developer ID certificate — effectively tricking OS X's built-in Gatekeeper security to believe that the files can be trusted and are not malicious.
Curiously, if the Mac Package installer, called Product.pkg, is located outside the DMG volume and the DMG volume Installer is unmounted, then you will receive a "Missing parameters" error.