Malicious code in bs58-33 (npm)
bs58-33 is a typosquat of the legitimate bs58 base58 codec that pulls in the malicious package base65-33x as a dependency. base65-33x clones base-x and exfiltrates all decoded strings (including cryptocurrency private keys and seeds) to a hardcoded C2 server before throwing an error. The attack was part of a coordinated six-package campaign published on 2026-08-11.
- Disclosed
- Last updated
- Blast radius
- Any npm project that installed bs58-33 or its sibling packages (bs58-15, bs58-77) during the publication window; downstream users of affected projects would inherit the exfiltration behavior.
- Ecosystems
- Attack vectors
- Affected entities
- bs58-33Typosquat wrapper that pulls in malicious base65-33x as a runtime dependency
- bs58-15Sibling typosquat wrapper published in the same campaign
- bs58-77Sibling typosquat wrapper published in the same campaign
- base65-33xMalicious sink package that exfiltrates decoded strings to C2 server
bs58-33 is a typosquat targeting the popular bs58 base58 codec library used in cryptocurrency tooling. The package itself contains no direct malicious code; instead, it simply requires and re-exports the malicious package base65-33x as a runtime dependency (declared as base65-33x: ^5.0.1).\n\nbase65-33x is a near-verbatim clone of the legitimate base-x library. Its decode() function exfiltrates every string passed to it by POSTing the raw input to a hardcoded C2 server at http://168.231.81.80:3002/api/log before throwing an error. Because base-x and bs58 are commonly used by cryptocurrency tooling to base58-decode private keys and seeds, the exfiltrated values frequently contain cryptographic secrets.\n\nbs58-33 and its sibling typosquats (bs58-15, bs58-77) were published alongside three base65 sink packages by a single npm maintainer account (smallmantis) within a ~90-minute window on 2026-08-11, forming a coordinated delivery-plus-exfiltration campaign. Installing bs58-33 is sufficient to introduce the key-exfiltration behavior into any dependent project.\n\nThe incident was reported by the OpenSSF malicious-packages project.
Indicators of compromise
- Packages
- bs58-33
- bs58-15
- bs58-77
- base65-33x
- IPs
- 168.231.81.80
Remediation
- Immediately remove bs58-33, bs58-15, and bs58-77 from all package.json files and lock files
- Audit npm install logs to identify all projects that installed these packages during the 2026-08-11 publication window
- For any project that installed these packages, assume all cryptocurrency private keys, seeds, and other secrets processed through base58 decoding have been exfiltrated; rotate all affected keys and secrets
- Review network logs for outbound POST requests to http://168.231.81.80:3002/api/log to confirm exposure
- Update to the legitimate bs58 package from the cryptocoinjs organization
- Implement npm package name allowlisting or dependency scanning to prevent typosquat installation
Sources
- GitHub Advisory GHSA-f8f3-v53p-w68x · GitHub Advisory Database
Cite this entry
"Malicious code in bs58-33 (npm)." supplychainattack.org, Supply Chain Attack Incident Catalog. Disclosed August 11, 2026; last updated August 14, 2026. https://supplychainattack.org/incident/malicious-code-in-bs58-33-npm-16vk79
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