An OS command injection vulnerability exists in Mako Server versions 2.5 and 2.6, specifically within the tutorial interface provided by the examples/save.lsp endpoint. An unauthenticated attacker can send a crafted PUT request containing arbitrary Lua os.execute() code, which is then persisted on disk and triggered via a subsequent GET request to examples/manage.lsp. This allows remote command execution on the underlying operating system, impacting both Windows and Unix-based deployments.