Apple is being sued for alleged negligence regarding its App Store security measures. In a lawsuit filed on Friday in the U.S. District Court of Northern California, three plaintiffs claim they were tricked into downloading and installing a fraudulent crypto wallet app, leading them to collectively lose more than $1.8 million.

The lawsuit centers on Apple’s claim that it secures its App Store by reviewing apps before they go live to protect users from fraudulent and malicious apps. In this case, the plaintiffs downloaded an app called Sparrow Wallet, even though the official Sparrow Bitcoin wallet is not available on iOS.

The plaintiffs transferred their Bitcoin to the fraudulent app, losing large amounts of the virtual currency, according to the complaint. Plaintiff James Ramirez lost about $875,000; plaintiff Christopher Ellis lost around $840,000, and plaintiff Jalen Delgado lost roughly $120,000.

The complaint targets one of Apple’s longtime competitive arguments: that its tight control over its App Store makes its platform safer than those offered by its rivals. The company has used this claim to push back against deregulation of the app ecosystem, including third-party app stores and sideloading.