What does the pdfjs-dist-fourth malware do?

The package pdfjs-dist-fourth was found to contain malicious code. The OpenSSF Package Analysis project identified 'pdfjs-dist-fourth' @ 10.0.33 (npm) as malicious. It is considered malicious because: - The package communicates with a domain associated with malicious activity. - The package executes one or more commands associated with malicious behavior.

Which versions of pdfjs-dist-fourth are malicious?

The following npm versions of pdfjs-dist-fourth are flagged malicious: 10.0.33. Treat any of these as compromised.

How do I remediate pdfjs-dist-fourth if I installed it?

Remove pdfjs-dist-fourth 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 pdfjs-dist-fourth — how do I know if it already compromised me?

If pdfjs-dist-fourth 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.

How do I find pdfjs-dist-fourth across my projects, lockfiles, and CI pipelines?

Search your lockfiles and build artifacts for pdfjs-dist-fourth (version 10.0.33).

Malicious package

pdfjs-dist-fourthnpm

Advisory published Mar 5, 2026Updated Mar 8, 2026

pdfjs-dist-fourth is a confirmed malicious npm package (MAL-2026-1257) that executes malicious code on install (malicious version 10.0.33). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in pdfjs-dist-fourth (npm)

MAL-2026-1257

Immediate action

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

npm uninstall pdfjs-dist-fourth

What this malware does

The package pdfjs-dist-fourth was found to contain malicious code.

The OpenSSF Package Analysis project identified 'pdfjs-dist-fourth' @ 10.0.33 (npm) as malicious.

It is considered malicious because:

The package communicates with a domain associated with malicious activity.
The package executes one or more commands associated with malicious behavior.

Malicious versions

1 flagged

10.0.33

Indicators of compromise (SHA-256)

e964b58935e9036b1bb97b860ed8de4789b4bc0af7fa624f201ce7c8f55ae0cf

fcaf355459e8baaef860a557036e51431e6eb6c44dcba0e800579cf978f2f64d

Detection & response playbook

Malicious package

Find it
Search your lockfiles and build artifacts for pdfjs-dist-fourth (version 10.0.33).
If you installed it — respond
Remove pdfjs-dist-fourth 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 pdfjs-dist-fourth 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. pdfjs-dist-fourth on npm has been identified as a malicious package (version 10.0.33 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Credits

Amazon Inspector · finder
OpenSSF: Package Analysis · finder

Detect & block this

O3 blocks pdfjs-dist-fourth-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

Explore

All malware advisories How O3 detects malware Vulnerability database