fix: fail fast when WEBHOOK_SECRET is unset or equals "development" - #41
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## Why Probot defaults its webhook secret to the literal string `"development"` when `WEBHOOK_SECRET` is unset. Without it, the bot **silently accepts forged webhooks signed with that trivially-known string** — a complete trust-boundary collapse on a misconfigured deploy. Wave-1 Security auditor flagged this as Bug #2 in `docs/agent-fleet/bugs.md`, the single highest-impact trust issue in the codebase. ## What New exported `assertWebhookSecret(env = process.env)` in `src/app.js`. Throws `Error` when `WEBHOOK_SECRET`: - is missing or empty - is whitespace-only - equals the literal string `"development"` (exact match — substrings like `"development-secret-9f2c"` are accepted, since they could be legitimate in a dev environment) `index.js` calls it after `mapLegacyEnvVars()` (so legacy `GITHUB_WEBHOOK_SECRET → WEBHOOK_SECRET` mapping happens first) and before `run(registerApp)`. The existing `try/catch` produces the standard `Error starting Probot:` console output and exits non-zero. `.env.example` updated with a comment explaining the constraint. ## Source Wave-1 Security auditor (Bug #2, `docs/agent-fleet/bugs.md`). ## Test plan - [x] 813 tests pass (was 806; +7 covering missing / empty / whitespace / exact-`development` / substring-`development*` / valid secret / reads-from-process.env-by-default) - [x] eslint clean - [ ] After deploy: stop pm2, unset `WEBHOOK_SECRET` in `/opt/temper/.env`, `pm2 start temper`. Bot should fail to start with a clear message instead of silently running with the fail-open default. ## Risk & rollout - Risk: low for any deployment that already has a real secret configured. Will fail-fast for misconfigured deploys, which is the point. - Rollout: self-update on merge. Operator must verify the env var is set before the bot tries to restart — the current netcup deploy already has it set. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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Fixes Bug #2 from
docs/agent-fleet/bugs.md— wave-1 Security auditor's #1 high-severity finding.Probot's webhook secret silently defaults to the literal
"development"when env unset, so a misconfigured deploy accepts forged webhooks. NowassertWebhookSecretthrows on unset / empty / whitespace / exact-development(substrings likedevelopment-secret-9f2cstill accepted).🤖 Generated with Claude Code