According to Huffington Post, "iPad has a security hole that allows anyone to freely download paid publications without dropping a cent."
"In just a few simple steps and a single word change, a user can make a bunch of publications show "download" instead of "buy." This'll actually allow the user to download free of charge. The single word is located in a .plist file. Once changed from "purchasable" to "viewable" iPad seems to be fooled into thinking that you don't have to pay to check out these apps."
Similar types of vulnerabilities can be found with other, non-publication apps as well.
Adobe, who manages both Wired and New Yorker iPad apps confirms the problem and vows to protect its content. "We've confirmed "it's possible for experienced users with detailed instructions to access some digital publications on the iPad that've not been purchased." We're working on a fix and expect to deliver a new version of our Digital Content Viewer to publishers on Friday, October 8."