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 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.

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?

Search your lockfiles and build artifacts for express-session-handler (version 2.3.3).

Malicious package

express-session-handlernpm

Advisory published Aug 21, 2026Updated Aug 21, 2026

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
Search your lockfiles and build artifacts for express-session-handler (version 2.3.3).
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 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

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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