praktor: Path traversal in Telegram file uploads allows writing outside the agent workspace uploads/ directory (stored instruction injection)

Impact

A remote Telegram user can write files to arbitrary paths inside an agent's persistent workspace volume (praktor-wk-<workspace>, mounted at /workspace/agent), escaping the documented uploads/ directory.

The attacker controls the Telegram document filename, which was concatenated into the destination path without sanitization (internal/telegram/bot.go, at both upload sites) and resolved with path.Join, which collapses ../ sequences. A filename like ../../../CLAUDE.md resolved to the root of the agent workspace volume, outside uploads/.

Because the agent workspace is the persistent working directory the Claude agent reads from and operates on across runs, writing outside uploads/ lets an attacker plant or overwrite files the agent later consumes — e.g. CLAUDE.md, agent instruction/skill/hook files, or other config under /workspace/agent. This turns a file upload into a stored injection into the agent's instruction/execution surface (CWE-22 path traversal escalating to stored instruction injection).