# MAL-2026-12656: Malicious code in cobrowsing-logger (npm)


- **Type:** Malicious package
- **Package:** `cobrowsing-logger` (npm)
- **Published:** 5 Aug 2026

## What is MAL-2026-12656?

MAL-2026-12656 is a malicious package in cobrowsing-logger, published on 5 Aug 2026. 

### Official description

index.js unconditionally requires _adapter.js on load. _adapter.js reconstructs destination hostnames from string-split fragments (assembling `oob-worker.cf99-9b3.workers.dev`, `oob-worker.cf102-baf.workers.dev`, `oob-worker.cf103-070.workers.dev`, `oob-worker.cf100-416.workers.dev`, and `sdk.dl.wel1.ru` / `ext.dl.wel1.ru` / `pkg.dl.wel1.ru` / `net.dl.wel1.ru` at runtime), platform-branches on the host OS, downloads an opaque executable over HTTPS with a DNS-TXT base64 fallback under the `*.dl.wel1.ru` zone, writes it to `/tmp` or `%TEMP%` under a decoy filename (`.cache_<hex>` on POSIX, `dotnet_diag_<hex>.exe` on Windows), chmods 0755, and spawns it detached via `/bin/sh -c` or `cmd.exe`. An opt-out branch is gated on generic-telemetry environment variables to mimic benign analytics behavior. The dropped binary is not shipped in the tarball and is not verified by hash or signature; whatever the operator of the Workers hosts / DNS-TXT channel serves at fetch time runs detached on the installer's machine on every `require('cobrowsing-logger')`.

## What should I do about MAL-2026-12656?

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-2026-12656 is a malicious package: cobrowsing-logger (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-2026-12656/ (Markdown: https://insights.sbomify.com/MAL-2026-12656/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/MAL-2026-12656

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From sbomify Insights: https://insights.sbomify.com/MAL-2026-12656/
Summaries are generated and may contain mistakes; the official description above is the record.