# MAL-2026-13747: Malicious code in base65-13x (npm)


- **Type:** Malicious package
- **Package:** `base65-13x` (npm)
- **Published:** 11 Aug 2026
- **Also known as:** GHSA-fp83-xcpx-v3qm

## What is MAL-2026-13747?

MAL-2026-13747 is a malicious package in base65-13x, published on 11 Aug 2026. 

### Official description

base65-13x@5.0.2 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.

## What should I do about MAL-2026-13747?

Remove the package from your dependencies and lockfiles, then rotate any secrets on machines where it was installed.

## Fix prompt for AI coding agents

```text
MAL-2026-13747 is a malicious package: base65-13x (npm). Every version was published to cause harm.

Task:
1. Search this repository's dependency manifests and lockfiles for the package, including transitive dependencies.
2. If it is present, remove it, regenerate the lockfile with the project's package manager, and replace whatever it was used for.
3. List any CI runners, developer machines or containers that installed it, so their secrets can be rotated.
4. If the package is not used anywhere, say so and change nothing.

Reference: https://insights.sbomify.com/MAL-2026-13747/ (Markdown: https://insights.sbomify.com/MAL-2026-13747/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/MAL-2026-13747

---
From sbomify Insights: https://insights.sbomify.com/MAL-2026-13747/
Summaries are generated and may contain mistakes; the official description above is the record.