• Execute repository content. Git object contents are never run. Hooks are gitbay's own binary, invoked by git; they compute facts and ask the daemon over a unix socket. Repo files are only ever read.
• Hold a signing key. There is no server-side signing key. "Verified" means a signature made by a key the user registered — the server never vouches for a commit it did not receive already signed. Merge commits the server creates are honestly unsigned.
• Serve repository HTML on its own origin as active content. Raw file serving is text/plain with nosniff. Rendered markdown/org is sanitized (bluemonday) and served under a CSP that forbids scripts.
• Put secrets in argv, URLs, or logs. Import and mirror credentials, registration invites, and API tokens travel on stdin or in request bodies, never as command arguments (visible in /proc) or query strings. Tokens are stored only as SHA-256 hashes.
• Confirm the existence of private repositories. Every surface answers "not found" identically for a private repo and a nonexistent one — web pages, git transport, control commands, release asset downloads.

• SSH public key = identity. The SSH username is ignored; the presented key's fingerprint resolves to an account. Key uniqueness is global.
• Per-instance trust. Email verification and key registration are local to an instance and never transfer. Account migration re-registers keys and re-verifies emails on the target by design.
• The control plane is one authenticated channel (SSH), fully usable from stock OpenSSH. The JSON API fronts the same command registry with bearer tokens minted only over SSH; git transport never runs over it.
• Anonymous surfaces — HTTPS clone of public repos, git:// where enabled, the read-only web UI — carry no credentials and expose only public data. HTTP push is refused via a pkt-line ERR, never a 401.

Every parser that eats bytes from a pusher, a key registrant, or an anonymous client has a fuzz target and must never panic:

• internal/protocol — the SSH command tokenizer (fuzzed against argv round-tripping).
• internal/gitd — the git:// pkt-line reader.
• internal/sig — the commit parser, the SSHSIG armor decoder and blob parser, and the OpenPGP armored-key reader.

Run deploy/audit.sh to exercise them plus go vet and govulncheck.

Tokens (web sessions, login links, email verification, API bearer tokens, deploy/CI) are random 256-bit values. Only their SHA-256 hash is stored, and verification is a database index lookup on that hash — the secret itself is never compared in Go, so there is no timing oracle to exploit. Webhook payloads are signed outbound with HMAC-SHA256; the forge verifies no inbound HMAC.

Anything that makes the server open an outbound connection to a user-supplied address — webhook delivery, GitHub-history import --api-base, mirror remotes — passes the same SSRF guard: the scheme must be http/https and, unless webhooks.allow_local is set, the resolved address must not be loopback, private, or link-local. The webhook dialer re-checks at connect time so a DNS answer that changes after validation still cannot reach private space. Redirects are never followed.

Rendered markup is attacker-controlled: a README, a wiki page and a profile's about text are all whatever someone pushed or typed. The risk is not only what the output contains but what the parser is willing to go and fetch — the filesystem counterpart of the SSRF guard above.

Org is rendered by go-org, whose default configuration resolves #+INCLUDE: and #+SETUPFILE: targets with os.ReadFile. Both are refused outright (orgConfig() in internal/httpd): the file is never opened and the keyword stays the inert text it already was, so the rest of the document renders normally. There is no safe subset to allow instead — an absolute path skips go-org's relative-path join, a relative one resolves against the daemon's working directory, and the content came from a git object rather than a checkout, so there is no directory to scope a read to. Markdown is goldmark, which has no include mechanism. go-org's parse warnings are discarded rather than logged, so pushed content cannot write to the server's log.

Org output is then sanitized (bluemonday UGC policy) because go-org passes raw HTML through — export blocks and inline export snippets — while goldmark drops it and needs no pass. The policy admits chroma's short token classes and nothing else.

Every response carries Content-Security-Policy (no scripts, no plugins, no embedding; inline styles allowed for chroma and label chips; images from any origin so external README images render), X-Frame-Options: DENY, X-Content-Type-Options: nosniff, Referrer-Policy: no-referrer, and Strict-Transport-Security when TLS is on. The UI needs no JavaScript, so script-src 'none' costs nothing.

• External images in rendered READMEs and profile about text load from their origin (no image proxy), which the author can use as a tracking pixel against a viewer. A profile is the wider surface of the two: it is linked from every commit and issue its owner touches. Documented; proxying is future work.
• Backups are consistent per the DB-snapshot-first ordering but are not a single atomic snapshot; a few orphaned git objects are possible and harmless (see Admin).
• A global signature-verification epoch over-invalidates the cache on any trust-input change. Correct, not a leak; a performance tradeoff.