The massive breach at LastPass was the result of one of its engineers failing to update Plex on their home computer, in what's a sobering reminder of the dangers of failing to keep software up-to-date.

The embattled password management service last week revealed how unidentified actors leveraged information stolen from an earlier incident that took place prior to August 12, 2022, along with details "available from a third-party data breach and a vulnerability in a third-party media software package to launch a coordinated second attack" between August and October 2022.

The intrusion ultimately enabled the adversary to steal partially encrypted password vault data and customer information.

The second attack specifically singled out one of the four DevOps engineers, targeting their home computer with a keylogger malware to obtain the credentials and breach the cloud storage environment.

This, in turn, is said to have been made possible by exploiting a nearly three-year-old now-patched flaw in Plex to achieve code execution on the engineer's computer, the streaming media service told The Hacker News in a statement.

The vulnerability in question is CVE-2020-5741 (CVSS score: 7.2), a deserialization flaw impacting Plex Media Server on Windows that allows a remote, authenticated attacker to execute arbitrary Python code in the context of the current operating system user.

"This issue allowed an attacker with access to the server administrator's Plex account to upload a malicious file via the Camera Upload feature and have the media server execute it," Plex said in an advisory released at the time.

The issue, which was discovered and reported to Plex by Tenable in March 2020, was addressed by Plex in version 1.19.3.2764 released on May 7, 2020. The current version of Plex is 1.31.1.6733.

"Unfortunately, the LastPass employee never upgraded their software to activate the patch," Plex said in a statement. "For reference, the version that addressed this exploit was roughly 75 versions ago."