Algernon selects its file handler from filepath.Ext() (engine/handlers.go:134), which does not treat the NTFS-equivalent names x.lua::$DATA, x.lua., or x.lua as .lua. On Windows, an unauthenticated client appends one of these suffixes to any server-side script on a public path and receives its raw source instead of executed output, leaking embedded secrets such as database credentials and the SetCookieSecret value. Linux and macOS hosts are unaffected.
When algernon is started with –domain (or –letsencrypt, which silently turns on –domain at engine/flags.go:372), the request handler resolves the served directory by joining the configured –dir with the value of the client-supplied Host header. The join is performed by filepath.Join with no validation, so a Host: .. header walks one level above the document root. Subsequent file resolution then exposes everything in that parent directory — arbitrary file read, …
The SSE event server's Access-Control-Allow-Origin response header was hardcoded to the wildcard * regardless of the caller's Origin. Because EventSource does not preflight and does not send cookies, the wildcard is sufficient to let any third-party page the developer visits open a cross-origin EventSource to the SSE port and read the live filename stream from JavaScript. Combined with the lack of authentication (advisory #2a), no further trickery is required — …
The SSE event server bound to 0.0.0.0:5553 on Linux/macOS by default because the platform-dependent host default in engine/flags.go:39-46 set host = "" for non-Windows, and utils.JoinHostPort("", ":5553") resolves to ":5553" — a Go http.Server.Addr of ":5553" listens on every interface. On Windows the same code chose "localhost", binding loopback only. The result was a platform split where the OS Algernon's dev workflow is most often used on (Linux/macOS) got the …
When Algernon is invoked with a single file path instead of a directory — the documented "quick demo" workflow (algernon foo.lua, algernon page.po2, algernon index.html, algernon mywebsite.alg) — singleFileMode is set to true and debugMode is forcibly enabled with no opt-out: // engine/config.go:498-502 // Make a few changes to the defaults if we are serving a single file if ac.singleFileMode { ac.debugMode = true ac.serveJustHTTP = true } debugMode activates …
When Algernon is asked for any URL path that resolves to a directory without an index file, DirPage walks upward through parent directories — past the configured server root — looking for a file named handler.lua to execute as the request handler. The loop terminates only after 100 ancestor steps or when filepath.Dir returns ., so on any absolute server-root path the search reaches the filesystem root (/ on Unix, …
When auto-refresh is enabled, Algernon spins up an SSE handler that streams a data: line for every filesystem event under the watched directory. The handler performs no authentication of any kind — no shared token, no cookie check against the permissions2 userstate, no IP allow-list, no path-prefix permission. Any client that can complete a TCP connection to the listener address receives the stream. This advisory covers the authentication gap in …