MalwarePublished 5 Aug 2026

claims-block-visibility (npm) · Malicious Code

Affects claims-block-visibilitySource GCVE Database

Malicious package : remove claims-block-visibility and rotate any secrets on hosts that installed it.

Data as of 5 Aug 2026, 16:07 UTC

Classification

Malicious package

Published to npm · OSV MAL-2026-12609

What to do

Remove claims-block-visibility from every project, lockfile and image that pulls it in. Treat any host that installed it as compromised: rotate the credentials, tokens and keys it could read, from a clean machine.

Affected software

Product	Affected	Fixed in
npmclaims-block-visibility	Affected =35.3.8	Fixed in–

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Description

The npm package 'claims-block-visibility' version 35.3.8 contains malicious code that executes automatically upon module load. It downloads and executes attacker-controlled native binaries from obfuscated and fallback DNS-based channels. This behavior results in silent execution of potentially harmful code on the host system without user consent.

Impact

Any application or environment that requires this specific version of the 'claims-block-visibility' package will execute attacker-controlled native code automatically, potentially leading to full system compromise, data theft, or further malicious activity. The execution is silent and obscured, increasing the risk of undetected compromise.

Defensive guidance

Users should immediately avoid using version 35.3.8 of 'claims-block-visibility'. Remove this version from all environments and replace it with a trusted, verified version or alternative package. Monitor for any unauthorized execution of binaries and consider forensic analysis if this version was previously used.

Summary

The 'claims-block-visibility' npm package (version 35.3.8) includes a malicious payload embedded in its index.js file. Upon requiring the package, it loads a polyfill script that selects an OS-specific endpoint to download a binary from obfuscated hosts under the *.workers.dev domain. If HTTPS is unavailable, it falls back to a chunked base64-over-DNS-TXT retrieval method from several .ru domains. The downloaded binary is saved to a temporary file with a disguised name, given executable permissions, and executed detached from the parent process using masked child_process calls. This results in immediate fetch-and-execute of opaque attacker-controlled native code on any system that imports this package.

References

npmjs.com/package/claims-block-visibility/v/35.3.8 (opens in a new tab)

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What to do

Affected software

Description

AI analysisMachine-generated, updated 5 Aug 2026, 16:07 UTC

Technical details

References

Community reviews