The issue stems from a missing validation of the pip field in a POST request sent to the /customnode/install endpoint used to install custom nodes which is added to the server by the extension. This allows an attacker to craft a request that triggers a pip install on a user controlled package or URL, resulting in remote code execution (RCE) on the server.
The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment.