Which versions of express-session-handler are malicious?

The following npm versions of express-session-handler are flagged malicious: 2.3.3. Treat any of these as compromised.

How do I remediate express-session-handler if I installed it?

Remove express-session-handler 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.

I already installed express-session-handler — how do I know if it already compromised me?

If express-session-handler 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 express-session-handler part of a known attack campaign?

Yes — express-session-handler is associated with the IN-MAL-2026-018494 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 express-session-handler 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 express-session-handler (version 2.3.3). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging express-session-handler across your stack and pipelines.

Malicious package

express-session-handlernpm

express-session-handler is a confirmed malicious npm package (MAL-2026-14345) that executes malicious code on install (malicious version 2.3.3). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in express-session-handler (npm)

MAL-2026-14345

Immediate action

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

npm uninstall express-session-handler

What this malware does

The package advertises itself as an Express session middleware but on module load unconditionally invokes an initPlugin() routine in index.js that performs an HTTPS fetch to https://api.jsonbin.io/v3/b/6a4f5816f5f4af5e29762c92, parses the response, extracts the record.cerookie field, and passes the resulting string to Function.constructor with require bound as an argument, executing attacker-controlled JavaScript in the installer's Node.js process. The remote document is mutable and controlled by whoever owns that jsonbin bin, so the code executed on any host that requires this module can be changed at any time. The file is prefaced with a '/*! normalize-path (ES6 safe version) */' header and ships an unused normalizePath helper alongside the loader, presenting a cover story unrelated to the actual behavior.

Malicious versions

1 flagged

2.3.3

Indicators of compromise (SHA-256)

0e94450f5541b39d8310a8b640dee027b0970db6e7cf724352726d49393bfb77

Detection & response playbook

Malicious package

Find it
Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for express-session-handler (version 2.3.3). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging express-session-handler across your stack and pipelines.
If you installed it — respond
Remove express-session-handler 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-session-handler 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-handler 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. express-session-handler on npm has been identified as a malicious package (version 2.3.3 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

IN-MAL-2026-018494

References

npmjs.com

Credits

Amazon Inspector · finder

Detect & block this

O3 blocks express-session-handler-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.

Malware detection Runtime egress monitoring

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