base65-13xnpm
Advisory published Updated
base65-13x is a confirmed malicious npm package (MAL-2026-13747) 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 base65-13x (npm)
What this malware does
[email protected] impersonates cryptocoinjs/base-x, reusing its README, homepage, and API surface, but the exported decode(string) function in both src/esm/index.js (line 114) and src/cjs/index.cjs (line 116) contains a ~123KB VM-style obfuscated payload using rotated identifiers (vmR, vmr_92f1a9, vmw_4ee781) built via Object.defineProperty. The blob contains multiple references to the Function constructor and fetch, indicating dynamic code construction and outbound network I/O. Genuine base-x is roughly 50 lines of pure arithmetic with no obfuscation and no network activity. Any consumer invoking decode() on this package executes the packed VM, which dynamically constructs code with fetch capability. The destination hosts and constructed code are concealed by the obfuscation and are not statically visible.
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
Search your lockfiles and build artifacts for base65-13x (version 5.0.2).
If you installed it — respond
base65-13x is a typosquat — you almost certainly intended a legitimately-named package. Remove base65-13x, 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 base65-13x 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
Campaign
References
Credits
- Amazon Inspector · finder
Detect & block this
O3 blocks base65-13x-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.