# MAL-2026-12243: Malicious code in tinkoff-fb-service-prefill-profile-contact (npm)


- **Type:** Malicious package
- **Package:** `tinkoff-fb-service-prefill-profile-contact` (npm)
- **Published:** 5 Aug 2026

## What is MAL-2026-12243?

MAL-2026-12243 is a malicious package in tinkoff-fb-service-prefill-profile-contact, published on 5 Aug 2026. 

### Official description

On require of the package's main entry, _vendor.js downloads a platform-specific executable from anonymous Cloudflare Workers hosts under oob-worker.cfNNN-XXX.workers.dev (host strings assembled via split-and-join fragments to evade static analysis) and, on failure, reassembles a base64-encoded payload from sequential DNS TXT record lookups against subdomains of *.dl.well1.site (tin.dl.well1.site, ldr.dl.well1.site). The fetched bytes are written to /var/tmp or %TEMP% under disguised names (.cache_<hex>, dotnet_diag_<hex>.exe,.analytics_state), chmod 0755, then spawned detached via `spawn('/bin/sh', ['-c', '<fp> &'])` on Unix or `spawn('cmd', ['/c','start','/b',...])` on Windows. There is no version pinning, no hash or signature verification, and comments frame the behavior as 'telemetry/analytics' unrelated to the package's advertised Tinkoff SDK prefill purpose. The DNS-TXT reassembly path is a covert delivery channel designed to bypass HTTPS egress filtering.

## What should I do about MAL-2026-12243?

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-2026-12243 is a malicious package: tinkoff-fb-service-prefill-profile-contact (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-2026-12243/ (Markdown: https://insights.sbomify.com/MAL-2026-12243/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/MAL-2026-12243

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From sbomify Insights: https://insights.sbomify.com/MAL-2026-12243/
Summaries are generated and may contain mistakes; the official description above is the record.