The research in this paper leads to the discovery of a series of high-impact security weaknesses, which enable a sandboxed malicious app, approved by the Apple Store, to gain unauthorized access to other apps’ sensitive data. More specifically, the researchers found that the inter-app interaction services, including the keychain and WebSocket on OS X and URL Scheme on OS X and iOS, can all be exploited by the malware to steal such confidential information as the passwords for iCloud, email and bank, and the secret token of Evernote.