Supply Chain Hardening

Supply-chain hardening

Defends a journalism toolchain against the dominant npm/bun supply-chain attack pattern: a maintainer account or CI pipeline is compromised, a malicious version ships, and machines install it before anyone notices. Recent example: the Mini Shai-Hulud TanStack attack (2026-05-11) compromised 84 versions across 42 @tanstack/* packages and exfiltrated AWS / GCP / Vault / GitHub / SSH credentials via a postinstall script.

The defense is layered and intentionally simple:

1. Install-time cooldown — only install package versions older than N days (default 7). This is the primary defense. By the time the cooldown expires, the security community has almost always flagged a compromised version and the registry has yanked it.
2. Sandboxed pre-install scan — when the cooldown has to be bypassed (CVE patch, fresh dep, urgent install), run the candidate tarball through a static-analysis scan that looks for the diagnostic signatures of supply-chain malware. The scan runs inside bwrap/firejail/unshare so a malicious package can't escape the inspection.
3. --ignore-scripts at install — postinstall is the #1 attack vector. Skip lifecycle scripts on every cooldown-bypass install.

These three together would have blocked the Mini Shai-Hulud TanStack attack on a stock laptop with no human in the loop.

Configure the cooldown

Verified config keys (npm v11+ and bun 1.3+):

| Manager | File | Key | Units | Exclusion key | |---|---|---|---|---| | npm | ~/.npmrc (or project .npmrc) | min-release-age | days | none yet — proposed in npm/cli#8994 | | bun | ~/.bunfig.toml (or project bunfig.toml) | [install] minimumReleaseAge | seconds | [install] minimumReleaseAgeExcludes = [] (exact names, no globs) |

Minimal config:

# ~/.npmrc
min-release-age=7

# ~/.bunfig.toml
[install]
minimumReleaseAge = 604800  # 7 days
minimumReleaseAgeExcludes = []

Requires npm 11+. Older npm silently ignores unknown keys, so the config looks correct but does nothing. Check with npm --version and npm config get min-release-age (should echo 7, not null).

Per-command bypass

When the cooldown blocks an install you actually want:

npm install @ --min-release-age=0 --ignore-scripts
bun add     @ --minimum-release-age=0 --ignore-scripts

The bun add --minimum-release-age=0 CLI flag works in 1.3+ even though the docs don't list it — it follows bun's bunfig key → kebab-case flag convention.

Always pair the bypass with --ignore-scripts. Postinstall is the most common payload-execution path in supply-chain malware (Mini Shai-Hulud, event-stream, ua-parser-js, coa, all used it). Native modules that legitimately need postinstall can have the script run manually after a human-readable review:

(cd node_modules/ && cat package.json | jq .scripts) # eyeball it
(cd node_modules/ && npm run postinstall)            # run if it checks out

When to scan before bypassing

The scan is for the dangerous moment: you've decided to bypass the cooldown and need a sanity check. The skill ships a reference script (scripts/hotpatch.example.sh) implementing the heuristics. Adapt it to your machine — Bash assumes bwrap (Linux); macOS users substitute sandbox-exec or skip the sandbox layer with the trade-off documented.

Static checks the scan should perform (each backed by a real attack):

| Check | Diagnostic of | Severity | |---|---|---| | optionalDependencies / dependencies containing github: or git+ URLs | Mini Shai-Hulud (delivered payload via github:tanstack/router# ref) | RED | | Large JS file at package root not referenced by main/module/exports/bin/files | Planted payload pattern (router_init.js in Mini Shai-Hulud) | RED | | Unpacked size >3x the prior stable version | Bulk payload smuggling | RED | | fileCount delta of 1–4 paired with >2x size jump | Single planted file | RED | | preinstall/install/postinstall/prepare scripts present | Lifecycle-script attack vector (event-stream, ua-parser-js, etc.) | YELLOW | | JS files referencing .ssh/, .aws/, .npmrc, GITHUB_TOKEN, AWS_SECRET, kube config | Credential exfiltration | YELLOW | | Version flagged deprecated in npm registry with "security"/"compromised"/"malicious" wording | Maintainer/registry yank | RED | | OSV.dev returns known vulnerabilities for @ | Disclosed CVE | RED (severity-dependent) |

Why prerelease versions are skipped from the size-delta baseline: dev/beta/rc versions have wildly different sizes than stable releases and produce false positives.

What the cooldown does not catch

Be honest about the limits with whoever you're configuring this for:

• Old packages with new malicious versions still in the cooldown window are blocked, but if the bad version also passes the cooldown (rare but possible — a compromise that goes >7 days undetected), the cooldown alone won't help. The scan catches most of those.
• Transitive deps. A clean ` you install can pull in a compromised transitive. Defenses: scan against the *resolved* tree (npm audit, osv-scanner`), and keep the cooldown active globally so transitive resolution also waits.
• npm ci against an existing lockfile. The cooldown applies during resolution, not installation of already-pinned versions. If your lockfile pins a compromised version, npm ci will install it. Mitigation: scan lockfiles in CI with osv-scanner --lockfile=package-lock.json.
• Pre-existing compromised packages in node_modules. Hardening protects future installs, not past ones. Audit existing deps separately (npm audit, osv-scanner, manual review of recently-published deps in your tree).

Quick-start workflow for a new machine

1. Verify npm >= 11: npm --version. If older, upgrade (sudo npm i -g npm@latest or tarball-swap if self-upgrade races).
2. Write ~/.npmrc and ~/.bunfig.toml with the config above.
3. Verify: npm config get min-release-age returns 7. cat ~/.bunfig.toml shows the [install] block.
4. Copy scripts/hotpatch.example.sh to ~/.claude/hotpatch.sh (or wherever fits). Make executable. Run ./hotpatch.sh --self-test against the synthetic Mini Shai-Hulud fixture (also shipped) to confirm the heuristics fire.
5. Document the bypass workflow somewhere your team will find it. The whole skill assumes the bypass is rare and reviewed, not the default.

Threat model: what this defends and what it doesn't

| Defends against | Doesn't defend against | |---|---| | Maintainer account compromise (npm token theft) | Targeted attack tailored to wait through the cooldown | | CI/CD pipeline hijack (Mini Shai-Hulud, valid OIDC tokens, SLSA-attested malice) | Compromise of a transitive dep already pinned in a lockfile | | Typosquatting (lookalike package names) — when paired with npm pkg fix and lockfile review | Malicious code in your own dev dependencies that you authored | | Postinstall payload execution (cooldown + --ignore-scripts = belt and suspenders) | Runtime supply-chain attacks (e.g., dynamic loading of bad code from a CDN) | | Drive-by npm install of a brand-new transitive | Compromise of the registry itself (very rare; out of scope) |

Further reading

• Original Mini Shai-Hulud StepSecurity analysis (TanStack attack, 2026-05-11):
• npm min-release-age config:
• bun minimumReleaseAge config:
• OSV.dev API (free, unauth):
• Earlier Shai-Hulud worm context:

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: jamditis
• Source: jamditis/claude-skills-journalism
• License: MIT
• Homepage: https://skills.amditis.tech/

Install and usage instructions live in the source repository linked above.