Which versions of string-format-kit are malicious?

The following npm versions of string-format-kit are flagged malicious: 1.0.1, 1.0.2. Treat any of these as compromised.

How do I remediate string-format-kit if I installed it?

string-format-kit is built to steal secrets, so assume every credential the build or runtime could read is compromised. Remove it from your project and lockfile, then rotate ALL exposed secrets — npm/registry tokens, cloud keys, CI/CD secrets, SSH keys, and any .env values — from a known-clean machine. Audit logs for unauthorized use of those credentials.

I already installed string-format-kit — how do I know if it already compromised me?

If string-format-kit was ever installed, its post-install/runtime payload may have already executed. O3's L7 egress monitoring and runtime eBPF sensors detect the credential exfiltration or command-and-control callback after install and block the malicious outbound channel, so you catch and contain the actual compromise — not just the presence of the package.

Is string-format-kit part of a known attack campaign?

Yes — string-format-kit is associated with the IN-MAL-2026-011046, IN-MAL-2026-014435 campaign. Packages in the same campaign often share infrastructure and payloads, so check whether any related packages are also in your dependency tree.

How do I find string-format-kit across my projects, lockfiles, and CI pipelines?

Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for string-format-kit (2 malicious versions). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging string-format-kit across your stack and pipelines.

Malicious package

string-format-kitnpm

string-format-kit is a confirmed malicious npm package (MAL-2026-11108) that steals credentials and exfiltrates sensitive data (malicious versions 1.0.1, 1.0.2). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in string-format-kit (npm)

MAL-2026-11108

Immediate action

Remove the package, then rotate any secrets the build/runtime could reach.

npm uninstall string-format-kit

What this malware does

The package's postinstall.js lifecycle script executes a shell pipeline via child_process.exec on npm install. The pipeline reads ~/.ssh/id_rsa, ~/.ssh/authorized_keys, ~/.ssh/known_hosts, ~/.aws/credentials, ~/.bash_history, the full process environment, and host reconnaissance output (whoami, hostname, id, sudo -ln, uname, /etc/os-release, /proc/1/cgroup, /.dockerenv, ps aux, ip addr, ls -la /), base64-encodes the aggregate, and transmits it via curl over plain HTTP to a hardcoded Burp Collaborator subdomain at pzs5w7ntzhsnepwk564lyfdci3oucl0a.oastify.com/d. The declared package purpose (string formatting) has no legitimate need to read the installer's SSH private keys or cloud credentials. The name resembles legitimate string-formatting libraries, consistent with typosquatting to lure installations.

The OpenSSF Package Analysis project identified 'string-format-kit' @ 1.0.2 (npm) as malicious.

It is considered malicious because:

The package communicates with a domain associated with malicious activity.
The package executes one or more commands associated with malicious behavior.

Malicious versions

2 flagged

1.0.11.0.2

Indicators of compromise (SHA-256)

752f3e4fded6d0546e00af595793134c025fd4afd8ee6d8188e0146a608b1cfb

d4ab7165e6602c9334efccd6113ccdd4edc62279e23d6a3cc8eb2f909e57a2ae

9e41e5ec29fcbb379f86d5a6167b42aec242fede681343996c198b1430e2dffa

Detection & response playbook

Credential / info stealer

Find it
Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for string-format-kit (2 malicious versions). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging string-format-kit across your stack and pipelines.
If you installed it — respond
string-format-kit is built to steal secrets, so assume every credential the build or runtime could read is compromised. Remove it from your project and lockfile, then rotate ALL exposed secrets — npm/registry tokens, cloud keys, CI/CD secrets, SSH keys, and any .env values — from a known-clean machine. Audit logs for unauthorized use of those credentials.
Did it already run?
If string-format-kit was ever installed, its post-install/runtime payload may have already executed. O3's L7 egress monitoring and runtime eBPF sensors detect the credential exfiltration or command-and-control callback after install and block the malicious outbound channel, so you catch and contain the actual compromise — not just the presence of the package.
How O3 protects you
O3 blocks string-format-kit before install through its supply-chain scanner, and if it has already run, detects and severs the exfiltration or C2 callback at runtime through L7 egress monitoring and eBPF.

Frequently asked questions

No. string-format-kit on npm has been identified as a malicious package (versions 1.0.1, 1.0.2 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

IN-MAL-2026-011046IN-MAL-2026-014435

References

Credits

Amazon Inspector · finder
OpenSSF: Package Analysis · finder

Detect & block this

O3 blocks string-format-kit-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the credential exfiltration and severs the channel.

Malware detection Runtime egress monitoring

Explore

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