A plugin pack for the DeepSeek Harness web profile: one human, one machine, one browser session. Loopback only, nothing that weakens the harness's authentication, zero npm dependencies, and no outbound request of its own except the pinned ffmpeg download below.

• Loopback only. The app binds 127.0.0.1; the CLI refuses an all-interfaces bind. Never put it behind a proxy, tunnel, port forward or published container port — that turns an authenticated surface into network-exposed code execution.
• The printed URL is a password (it carries the launch token). Never paste it into a chat, an issue, a screenshot or a recording.
• No secrets in this repository, enforced not promised: credentials live in $DSH_HOME/.credentials.yaml, outside this tree, and scripts/checks/check-no-secrets.mjs fails on a credential-shaped file before it can be committed.
• Nothing patches core: every plugin is a standard dsh bundle, and every route it adds sits behind the harness's own session check.
• Zero npm dependencies, vendored engines pinned by hash, no telemetry, no auto-update, no HTTPS server. Writes go only under $DSH_HOME, the session workspaces you open, and the Desktop for the two features that save a picture there.
• Personal tooling, one trust domain — not multi-tenant. Security fixes land on main as alpha bumps; there are no maintenance branches.

Supported: main, and the harness line pinned in .dsh-version.json (0.2.0-rc.2); any other published line is not tested and not claimed. dsh-rightbar, dsh-rightbar-files and dsh-open-in-app are forks of that line's client bundles, so a line bump is deliberate: bump the pin, run scripts/sync-vendored.ps1, re-verify. The pack targets the web profile only, stays alpha until promoted, and its installer is idempotent — uninstall removes only the bundle, its patch layer and the skill folders it wrote (each marked .vncode-<package>).

Report privately: on GitHub, Security → Report a vulnerability in vecnode/vncode. Include the package and version, the harness line you tested, the impact, and reproduction steps if they are safe to share. Best-effort acknowledgement within 3 business days; credit on request.

Good-faith research on your own installation is welcome — no attacking other people's instances, no data that is not yours, no destructive or denial-of-service tests, no social engineering. Out of scope here (report upstream): bugs in @deepseek-ai/dsh-* itself, model behaviour, the LLM provider, the harness's own sandbox and file policy, and anything needing root/administrator, physical access, a compromised OS or browser, or an already-unlocked session.

The asset is your machine behind one browser session: the files the model's tools can reach, the workspace, conversation history, model API credentials, and the harness's own shell surfaces. The boundary is plain HTTP over loopback, authenticated by a session cookie minted from a per-process launch token — everything the pack adds is mounted through the harness's own connection service and inherits that gate instead of inventing one. Every surface follows one shape: an exact-path route behind that fence, read-only where possible, argv-only spawns with a deadline, realpath containment, and writes that are create-exclusive under host-generated names (the package READMEs list the per-surface guards).

Not defended against: root/administrator, a compromised OS/browser/extension, a person with your unlocked session, and — the important one — deliberate exposure. Bind a LAN interface, forward the port or add a tunnel and the cookie is all that stands between that network and your machine.

Five layers, all the pinned line's own code; the pack only registers routes behind them. The bind is 127.0.0.1 (the CLI refuses --host 0.0.0.0). The launch token is 32 random bytes per process, printed as the only authentication input; GET /?token=… exchanges it (timing-safe) for a cookie and answers 303. The session cookie is dsh-auth-<hash(authority)> valued v1.<payload>.<HMAC-SHA256>, Path=/; HttpOnly; SameSite=Strict, 30-day Max-Age by default (cookieMaxAgeDays on the connection row). The Host/Origin fence answers 403 for a foreign authority or a cross-site fetch and 401 for failed authentication. The index gate serves index.html only to a session; the JS/CSS bundles are public and contain no secrets. The signing secret lives in $DSH_HOME/.credentials.yaml, written 0600, and the harness refuses to boot if that file is group/other-readable on POSIX.

1. Keep it on loopback: the pack's launcher or npx @deepseek-ai/dsh@0.2.0-rc.2 web, no --host, no --trusted-host. Loopback traffic does not cross a firewall, so no firewall rule "fixes" an exposed bind.
2. Treat the printed URL as a password, and stop the app when you are not using it.
3. Know what logs out: stopping the app kills the launch token; deleting the site's cookies ends that browser's session; a different port invalidates cookies (name and audience derive from host:port); a plain restart does not log anyone out — the signing secret is durable.
4. Rotate the secret to revoke every cookie at once: stop the app, delete only the client-connection/browser-session entry from $DSH_HOME/.credentials.yaml (it also holds your model keys), save, restart. To shorten sessions instead, set cookieMaxAgeDays on the connection row in $DSH_HOME/profiles/web/cordis.patch.yml — a patch replaces the row's whole config, so restate what you rely on.
5. Harden the machine — loopback is only as private as the box: run as your own user (never root/administrator), patch the OS and browser, use disk encryption, lock the screen. "Locked" does not mean hidden from a local process or user, does not protect an unlocked screen, and does not sandbox the model's tools (that is the harness's own file policy).

# 1. Loopback and nothing else. Expect 127.0.0.1, never 0.0.0.0.
ss -ltnp | grep 3080                     # Linux
lsof -nP -iTCP:3080 -sTCP:LISTEN         # macOS

# 2. Unauthenticated access is refused. Expect 401 and a one-line body.
curl -i http://127.0.0.1:3080/api/dsh-cmdbar/activity
curl -i http://127.0.0.1:3080/            # the index answers 401 too

# 3. The fence works. Expect 403 for a foreign authority and for a cross-site claim.
curl -i -H 'Host: evil.example' http://127.0.0.1:3080/api/dsh-cmdbar/activity
curl -i -H 'Sec-Fetch-Site: cross-site' http://127.0.0.1:3080/api/dsh-cmdbar/activity

Windows: Get-NetTCPConnection -LocalPort 3080 -State Listen. Then in DevTools → Application → Cookies the dsh-auth-… entry must show HttpOnly, SameSite=Strict, Path=/ and an expiry about 30 days out. A 401 on step 2 and a 403 on step 3 are the whole model working; the parts that are the pack's own are pinned by node scripts/checks/check-node-routes.mjs.

dsh web prints one line once it is listening: dsh web: http://127.0.0.1:3080/?token=<launch token>. The token is exchanged for the session cookie, and everything after rides the cookie. The pack's launchers (scripts\run-web.bat → scripts/run-web.ps1, scripts/run-web.sh) read it in memory and never write it to a file (the POSIX half streams through an anonymous FIFO for exactly that reason), never echo it, hand it to the browser as one argv element (never a command string, so nothing in it reads as a shell metacharacter), and open the URL only when it names a loopback address (127.0.0.1, ::1, localhost; on Windows only a literal 127.x.x.x, so 127.evil.com is refused). --no-open is passed so the hand-off happens once. The token dies with the process (restart to kill a leaked URL); the cookie is signed with a durable secret, so a restart does not log a browser out — rotate the secret for that.

• Nothing to trust at install time: no shipped package declares a runtime dependency, and the bundles are installed as live links.
• Vendored engines are pinned and hashed: CodeMirror 6, Mermaid and pdf.js are built from their vendor/ folders and served by the packages themselves — no CDN, no runtime download. Each records a sha256 per file and a digest in lib/vendor/…/VERSION.json, re-hashed offline by build.mjs --check; forked bundles carry a GENERATED banner and are checked by scripts/sync-vendored.ps1 -Check.
• One binary may be downloaded, and only when the machine has none: ffmpeg. The repository ships a pin (packages/dsh-media/lib/binaries.json: official URL plus SHA-256 per platform-arch), never a 130–170 MB build. PATH wins; the archive is hashed as it arrives and compared with the pin before anything is executed; a mismatch installs nothing; unpacking uses the host's own tar and a .partial file is renamed into place; DSH_MEDIA_NO_INSTALL=1 forbids the download entirely. darwin-arm64 is deliberately unpinned (no Apple-Silicon build publishes both a URL and a checksum; a pin that moves is worse than an honest gap).
• Security-relevant behaviour is pinned by tracked checks: workspace containment, create-only writes, git option-injection refusal, screenshot refusals, diagram budgets, and the ffmpeg provisioning pipeline against a synthetic archive.

A secret in a commit is public for as long as the repository exists — in every fork, clone and cache. scripts/checks/check-no-secrets.mjs, run by hand before anything ships, scans exactly what git add -A would stage and fails on a key-shaped string, a credential assignment (quoted name or not), a launch token in a URL, a Google/Firebase api key, a GitHub/AWS/Slack/Stripe key, a private-key block or a bearer JWT, plus a missing .gitignore credential rule. It never prints what it found (file, line, rule and a masked preview only), its allowlist is empty by design, and it self-tests that it fires.

A vendored bundle carries its author's credentials. The Canvas tab's vendored Excalidraw (removed in alpha.13) shipped its OSS Firebase config — Google api key included, and Firebase web api keys are public by design — so vendoring it put a google_api_key in this public repository and GitHub's scanning opened a public leak alert naming Excalidraw's key, which this repository can neither rotate nor revoke. The fix is a build patch, never an allowlist entry: a patch under the engine's own vendor/<name>/patches/ blanks the apiKey value in every file read from the pinned package's dist/, matched by key name so a rotated key is redacted the same. Read what a third-party build ships before committing it. If a credential is ever committed: rotate it first (assume it is public), then remove it from history (git filter-repo or the BFG) and force-push — deleting the file in a new commit does not remove it. Enable GitHub's secret scanning and push protection as a second net.

• No API keys are read: $DSH_HOME/.credentials.yaml is touched for presence only — a boolean, never a value.
• No way to weaken the harness's authentication, and no flag, setting or variable that turns the session check off.
• No WebSocket upgrade and no shell of any kind — the dock is a read-only transcript, and shells come from the harness's own terminal tabs.