A pinned version is a fixed commit, tag, or release reference used to ensure the same code is installed again later. Instead of tracking a moving branch such as main, the client or build system records one exact revision and reuses it for repeatable installs.
This matters in cyber security because pinning is meant to reduce supply-chain risk: reviewers can inspect one known codebase, then expect the deployed software to match it. However, a pin only protects users if the client also verifies the final checkout on disk. If a repository owner can swap content after approval, or if the installer re-resolves a reference without integrity checks, a supposedly trusted plugin may become malicious after review. Defenders use pinned versions, checksum validation, and client-side verification to detect version drift and stop tampering before code is executed.