classbreeze-utilsnpm
classbreeze-utils is a confirmed malicious npm package (MAL-2026-5973) that opens a backdoor for remote access (malicious versions 0.7.7, 0.7.8, 0.7.9…). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in classbreeze-utils (npm)
What this malware does
The package masquerades as a Tailwind plugin: README and the top of src/index.js are a verbatim clone of @tailwindcss/typography (require('tailwindcss/plugin'), prose-* class generator), even though the package name has no relationship to Tailwind. Appended after the cloned plugin code at src/index.js:124+ is a heavily obfuscated IIFE using an RC4-decoded string array and AES-decipher key table to hide its strings and control flow. The decoded action table contains keys 'cmd.npx', 'cmd.npxwin', 'pkg.link', 'cmd.install', 'flag.yes', which are consumed by helpers that call child_process.spawn with detached:true, stdio:'ignore', windowsHide:true and creationFlags set to DETACHED_PROCESS to silently run npx -y <pkg.link>, fetching and executing an attacker-controlled package from the npm registry on the developer's machine. On Windows an additional path uses keys 'ext.vbs', 'vbs.tag', 'win.wscript': a VBS file is written to os.tmpdir() with a crypto.randomBytes(4) hex prefix and launched via wscript.exe (detached, windowsHide), followed by process.exit(0), to hide the dropper invocation from the console. The action table also contains 'env.api' and 'api.base' entries, and the spawn helper clones process.env and injects api.base as the env.api value into the child, so the downstream npx-fetched package receives a C2/telemetry endpoint via environment. Because require('classbreeze-utils') is the plugin entry point loaded by any Tailwind build that adds it, the dropper fires automatically as soon as a build that depends on it runs, executing arbitrary attacker-controlled code on the developer/CI machine.
Any computer that has this package installed or running should be considered fully compromised. All secrets and keys stored on that computer should be rotated immediately from a different computer. The package should be removed, but as full control of the computer may have been given to an outside entity, there is no guarantee that removing the package will remove all malicious software resulting from installing it.
Malicious versions
Indicators of compromise (SHA-256)
Detection & response playbook
Backdoor / remote accessFind it
Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for classbreeze-utils (4 malicious versions). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging classbreeze-utils across your stack and pipelines.
If you installed it — respond
classbreeze-utils establishes remote access, so treat any host that installed it as fully compromised. Isolate the machine, remove the package, rotate all credentials it could reach, and rebuild from a trusted image rather than cleaning in place — a backdoor may have planted additional persistence.
Did it already run?
If classbreeze-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 classbreeze-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 classbreeze-utils-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the C2 callback and severs the channel.