# MAL-2026-6531: Malicious code in @appupdate/cdn-sync (npm)


- **Type:** Malicious package
- **Package:** `@appupdate/cdn-sync` (npm)
- **Published:** 26 Jun 2026

## What is MAL-2026-6531?

MAL-2026-6531 is a malicious package in @appupdate/cdn-sync, published on 26 Jun 2026. 

### Official description

Package @appupdate/cdn-sync ships as a thin koffi wrapper around prebuilt Go cgo native libraries (~12MB linux.so, ~11MB darwin.dylib for x64/arm64). The JS surface exports `ProbeStart(knock)` / `ProbeStop` / `ProbeRunning` / `ProbeLastError`, where `ProbeStart` requires a caller-supplied passphrase that must match a value compiled into the native binary (per the source comment: 'knock must match the BuiltinKnock compiled into native'). The README explicitly states that endpoints and authentication are encapsulated inside the native binary so installers cannot inspect them. Strings inside the shipped binaries reference Tencent Cloud Object Storage endpoints (`cos.myqcloud.com`, `tencentcos.cn`, `https://%s.cos.%s.myqcloud.com`), indicating the worker is linked against the Tencent COS SDK with destination bucket and credentials embedded in opaque bytes. The advertised purpose (CDN static-asset sync) does not match the only exported symbol family (`Probe*`), and publisher metadata is an unfilled placeholder (`github.com/your-org/appupdate.git`, license UNLICENSED, generic `@appupdate` scope) providing no verifiable identity. The combination of a passphrase-gated activation path, deliberately hidden destination and credentials inside a shipped binary, doc-mismatched cover story, and placeholder publisher metadata is the structural shape of a covert uploader / backdoor: once an installer or downstream caller invokes `ProbeStart` with the right knock, attacker-controlled code executes on the installer's machine against a Tencent COS bucket the installer cannot see or audit.

## What should I do about MAL-2026-6531?

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-2026-6531 is a malicious package: @appupdate/cdn-sync (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-2026-6531/ (Markdown: https://insights.sbomify.com/MAL-2026-6531/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/MAL-2026-6531

---
From sbomify Insights: https://insights.sbomify.com/MAL-2026-6531/
Summaries are generated and may contain mistakes; the official description above is the record.