In a recent development that underscores the ongoing battle between cybersecurity and malicious actors, researchers have unveiled a zero-day exploit targeting the Telegram messaging app on Android devices. This vulnerability, identified by the Slovakia-based cybersecurity firm ESET and dubbed “EvilVideo,” could have enabled attackers to send harmful payloads masquerading as legitimate multimedia files.
Details of the Exploit
The exploit was discovered on an underground forum in early June, where it was being sold by a user known as “Ancryno.” The seller showcased the exploit through screenshots and a video demonstrating its functionality within a public Telegram channel. This exploit leveraged Telegram’s default setting, which automatically downloads media files, allowing attackers to send malicious payloads through channels, groups, and chats.
While users could manually disable the automatic download feature, the risk remained if they inadvertently tapped the download button for a shared file. Upon attempting to play what appeared to be a video, users would receive a message indicating that the file could not be played, with a suggestion to use an external player. This is where the malicious intent lay; hackers had disguised a harmful application as this external player.
Fortunately, Telegram addressed this vulnerability in versions 10.14.5 and above, released earlier this month. In the updated version, any malicious file shared in a chat is now accurately displayed as an application, rather than a video, thereby mitigating the risk of inadvertent installation.
Potential Impact and Unknowns
Despite the patch, the exploit had a window of approximately five weeks during which it could have been exploited. However, ESET has not confirmed whether it was actively used in the wild. The identity of the hacker group or individual behind this exploit remains unclear, as does their intended use for it and its overall effectiveness.
Adding another layer of intrigue, the same underground forum account that advertised the EvilVideo exploit has also promoted Android cryptomining-as-a-service malware, claiming it to be fully undetectable. This raises further questions about the capabilities and intentions of those operating in the shadows of the digital landscape.
