Malicious code in base99-85x (npm)
base99-85x is a typosquat of the base-x npm package that exfiltrates decoded input to a hardcoded HTTP endpoint. The malicious decode() function POSTs every caller-supplied string to http://168.231.81.80:3001/api/log in cleartext, exposing sensitive material such as private keys and wallet seeds.
- Disclosed
- Last updated
- Blast radius
- All npm consumers of base99-85x package
- Ecosystems
- Attack vectors
- Affected entities
- base99-85xTyposquat of base-x library; malicious decode() function exfiltrates caller-supplied strings
base99-85x is a typosquat package published to npm that mimics the legitimate base-x encoding library. The package's main export contains a malicious decode() function that intercepts all decoding operations.
When decode() is called with any input string, the function POSTs that string as JSON ({"text": }) to the hardcoded plain-HTTP endpoint http://168.231.81.80:3001/api/log before returning the decoded buffer. This exfiltration occurs in cleartext without user knowledge or consent.
The malicious relay is implemented via an inline msgLog helper in both CommonJS and ESM build outputs, ensuring the exfiltration fires regardless of whether consumers load the package via require() or import. Since callers of base-x commonly pass base58/base64-encoded secret material such as private keys, wallet seeds, and cryptographic payloads, any such input decoded through this package is transmitted to the operator of 168.231.81.80.
The incident was identified by the OpenSSF malicious-packages project and reported via GitHub Advisory GHSA-6h69-gw54-v5hv.
Indicators of compromise
- Packages
- base99-85x
- IPs
- 168.231.81.80
Remediation
- Immediately remove base99-85x from all dependencies and package-lock.json files
- Audit all code that may have used base99-85x to identify if sensitive material (private keys, wallet seeds, cryptographic payloads) was decoded through this package
- If sensitive material was decoded through base99-85x, assume it was exfiltrated and rotate all affected credentials, keys, and secrets
- Replace base99-85x with the legitimate base-x package
- Review npm audit logs and dependency trees for any other typosquat or suspicious packages
- Monitor for unauthorized access or transactions using any credentials that may have been exposed
Sources
- GitHub Advisory GHSA-6h69-gw54-v5hv · GitHub Advisory Database
Cite this entry
"Malicious code in base99-85x (npm)." supplychainattack.org, Supply Chain Attack Incident Catalog. Disclosed August 19, 2026; last updated August 19, 2026. https://supplychainattack.org/incident/malicious-code-in-base99-85x-npm-95t6wq
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