base65-11xnpm
base65-11x is a confirmed malicious npm package (MAL-2026-13745) that typosquats a legitimate package to trick installs (malicious version 5.0.2). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in base65-11x (npm)
What this malware does
base65-11x is a name-lookalike of the widely used base-x encoder. Both entrypoints (src/cjs/index.cjs and src/esm/index.js, ~127KB each vs. ~4KB for real base-x) contain the legitimate base-x source followed by a ~123KB single-line obfuscated payload wrapped in a custom-VM IIFE (identifiers vmN, vmA_ab9191, vmU_d6a896; Object.defineProperty-based dispatch on a global slot). The payload sits at module top level, so it executes automatically whenever a consumer require()s or import()s the package. A pure base-encoding utility has no functional need for runtime-VM-packed code on load, and the payload is duplicated across CJS and ESM entrypoints to ensure execution regardless of module system. The specific payload behavior is concealed inside the VM interpreter and cannot be recovered without executing it.
Any computer that has this package installed or running should be considered fully compromised. All secrets and keys stored on that computer should be rotated immediately from a different computer. The package should be removed, but as full control of the computer may have been given to an outside entity, there is no guarantee that removing the package will remove all malicious software resulting from installing it.
Malicious versions
Indicators of compromise (SHA-256)
Detection & response playbook
TyposquatFind it
Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for base65-11x (version 5.0.2). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging base65-11x across your stack and pipelines.
If you installed it — respond
base65-11x is a typosquat — you almost certainly intended a legitimately-named package. Remove base65-11x, install the correct package, and rotate any secrets exposed during the install since post-install scripts may have already run.
Did it already run?
If base65-11x was ever installed, its post-install/runtime payload may have already executed. O3's L7 egress monitoring and runtime eBPF sensors detect the credential exfiltration or command-and-control callback after install and block the malicious outbound channel, so you catch and contain the actual compromise — not just the presence of the package.
How O3 protects you
O3 blocks base65-11x before install through its supply-chain scanner, and if it has already run, detects and severs the exfiltration or C2 callback at runtime through L7 egress monitoring and eBPF.
Frequently asked questions
Campaign
References
Credits
- Amazon Inspector · finder
Detect & block this
O3 blocks base65-11x-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.