express-devernpm
Advisory published Updated
express-dever is a confirmed malicious npm package (MAL-2026-13368) that executes malicious code on install (malicious versions 5.1.7, 5.1.8). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in express-dever (npm)
What this malware does
[email protected] registers postinstall: node index.js in package.json, and index.js is heavily obfuscated (obfuscator.io-style rotated string array with RC4/base64 decoders, hex-numeric constant folding, _0x variable naming, control-flow flattening). Decoded, the script requires axios/fs/path/child_process/os, constructs a dotted-quad host string at runtime via repeated .concat(x, '.') calls, performs axios.get(<url>), writes the response body to a file under process.cwd() with {flag:'w+'}, and spawns the written file via child_process with windowsHide:true. This is a download-and-execute dropper that fires automatically on npm install. Corroborating signals: package.json declares a self-referential floating dependency (express-dever: ^5.1.7), author and description fields are blank, and the README instructs readers to sandbox the file — consistent with a throwaway malicious upload rather than a legitimate library.
Malicious versions
Indicators of compromise (SHA-256)
Detection & response playbook
Malicious packageFind it
Search your lockfiles and build artifacts for express-dever (2 malicious versions).
If you installed it — respond
Remove express-dever 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 express-dever was installed, its post-install payload may already have run. Removing the package does not undo that — check outbound connections and credential use from the install window onward.
Frequently asked questions
Campaign
References
Credits
- Amazon Inspector · finder
Detect & block this
O3 blocks express-dever-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.