Element Desktop 1.9.6 and earlier depend on a vulnerable version of Electron, leading to a High severity vulnerability in Element Desktop, relating to its functionality for opening downloaded files. If successfully exploited, the vulnerability allows an attacker to open an arbitrary file path on the user's machine using the platform's standard mechanisms, but without the ability to pass additional arguments or data to the program being executed.
However in certain platform configurations, the same vulnerability could allow an attacker to open an arbitrary URL with an arbitrary scheme instead of a file path, again using the platform's standard mechanisms. There has been research demonstrating that the ability to open arbitrary URLs can sometimes lead to arbitrary code execution.
The attack requires user interaction and the exploit is complex. To the best of our knowledge, the vulnerability has never been exploited in the wild.
Patched in 1.9.7 with further hardening done in 1.9.9 to ensure it's harder to exploit even in light of new Electron vulnerabilities. Please upgrade to 1.9.9 as soon as possible. The vulnerability has been assigned CVE-2022-23597.
Discovered and reported by Sirius and TheGrandPew.