Tenable says customers must manually upgrade their software to revive Nessus vulnerability scanner agents taken offline on December 31st due to buggy differential plugin updates. [...]
source https://www.bleepingcomputer.com/news/security/bad-tenable-plugin-updates-take-down-nessus-agents-worldwide/
source https://www.bleepingcomputer.com/news/security/bad-tenable-plugin-updates-take-down-nessus-agents-worldwide/