The BlackBerry World app before 5.0.0.262 on BlackBerry 10 OS 10.2.0, before 5.0.0.263 on BlackBerry 10 OS 10.2.1, and before 5.1.0.53 on BlackBerry 10 OS 10.3.0 does not properly validate download/update requests, which allows user-assisted man-in-the-middle attackers to spoof servers and trigger the download of a crafted app by modifying the client-server data stream.