This vulnerability allows for code execution via a deserialisation vulnerability within the react-server-dom packages. This will affect React, NextJS and downstream projects who utilise these frameworks.
AssetNote released a technical research post and detection technique which is effective at identifying unpatches instances, where as full RCE chains may fail due to WAF's fingerprinting those payloads and bypasses heavily. Vercel's CEO released a simple breakdown of the issue and how it works.
We have witnessed widespread exploitation activity for this vulnerability, especially exploiting this to deploy an in-memory webshell. There has been some community efforts to detect exploitation activity, however exploiting this vulnerability usually leaves little to no trace which is difficult for defenders.
Patching immediately is the only effective strategy for dealing with this vulnerability.