Apple provides a system for developers to prevent piracy of their applications: When an app is launched, it checks to see that it’s authorized do so on the computer—if not, the user will then be prompted to enter the Apple ID and password that were used to buy the app. This process is called ‘receipt validation’ and it works much as security does in a brick-and-mortar retail store, by checking to make sure you have a receipt before you walk out the door with merchandise.

The problem is, while Apple has created this system, it’s incumbent upon the developers to remember to implement it in their own application. Some developers don’t, and that’s where the risk of piracy comes in.

According to the supposed hack, you can get applications purchased by other users to run on your Mac by deleting certain files inside the application’s package and replacing them with files from an app that you’ve legitimately downloaded—it doesn’t even have to be a paid app. The example that’s making the rounds uses the files from Twitter, a free download, and inserts them into the application package for the popular game Angry Birds, a $5 purchase.

, Angry Birds checks for a valid receipt—but doesn’t check to make sure that receipt Angry Birds itself. Think of it as the equivalent of hopping theaters at the local multiplex: you may have a genuine ticket, but it may not be for the movie you’re about to see—it just depends on how closely the usher looks at it.