express-session-jsnpm
Malicious code in express-session-js (npm) Remove it immediately and rotate any exposed credentials.
What this malware does
Package impersonates legitimate express-session package; initPlugin() downloads and executes attacker-controlled remote code on startup via new Function.constructor()
The package express-session-js was found to contain malicious code.
Malicious versions
Every published version of this package is considered malicious — remove it entirely.
Indicators of compromise (SHA-256)
Detection & response playbook
TyposquatFind it
Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for express-session-js (all published versions). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging express-session-js across your stack and pipelines.
If you installed it — respond
express-session-js is a typosquat — you almost certainly intended a legitimately-named package. Remove express-session-js, install the correct package, and rotate any secrets exposed during the install since post-install scripts may have already run.
Did it already run?
If express-session-js 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 express-session-js 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
References
Credits
- Amazon Inspector · finder
- SafeDep · finder
Detect & block this
O3 blocks express-session-js-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.