blue-string-formatter-utilsnpm
blue-string-formatter-utils is a confirmed malicious npm package (MAL-2026-16273) that executes malicious code on install (malicious version 1.0.0). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in blue-string-formatter-utils (npm)
What this malware does
The package advertises itself as 'Utility helpers for string formatting' but its shipped main file performs a single behavior: an XMLHttpRequest GET to the protocol-relative URL //xss.report/c/k3rne111 whose response body is passed directly to eval(). Any require()/import of this package causes arbitrary attacker-controlled JavaScript from xss.report to execute in the consumer's Node process, with no pinning, no integrity check, and no relationship to the advertised functionality. The mismatch between the package's stated purpose (string utilities) and its actual contents (a remote-code loader) is a cover-story pattern.
Malicious versions
Indicators of compromise (SHA-256)
Detection & response playbook
Malicious packageFind it
Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for blue-string-formatter-utils (version 1.0.0). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging blue-string-formatter-utils across your stack and pipelines.
If you installed it — respond
Remove blue-string-formatter-utils from your project and lockfile, then assume any secrets accessible to the build or runtime were exposed: rotate API keys, tokens, and credentials, and audit for unexpected outbound activity or persistence.
Did it already run?
If blue-string-formatter-utils 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 blue-string-formatter-utils 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
Campaign
References
Credits
- Amazon Inspector · finder
Detect & block this
O3 blocks blue-string-formatter-utils-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the malicious outbound activity and severs the channel.