HTTP PUT is a request method used to create a new resource at a known URI or replace an existing one with the content sent in the request body. In practice, it is common in APIs, file management systems, and WebDAV-style uploads. PUT is usually designed to be idempotent, meaning repeated identical requests should produce the same final server state.
In security work, PUT matters because it gives a client write access to a server endpoint. If authentication, authorization, or input handling is weak, attackers may abuse PUT to upload web shells, overwrite files, stage malicious payloads, or move stolen data. Defenders also watch for suspicious PUT patterns such as stable URIs, repeated uploads, unusual chunked transfer coding, or traffic from processes that should not be writing to remote services. The method itself is legitimate; the risk comes from how and where it is used.