Android’s regular security update for December 2017 included a fix for a serious vulnerability that could allow attackers to modify installed apps without affecting their signature. This would allow an attacker to gain access to the affected device (indirectly). First found by researchers in July, this vulnerability (designated as CVE-2017-13156, and also called the Janus vulnerability) affects versions of Android from 5.1.1 to 8.0; approximately 74% of all Android devices have these versions installed.