# MAL-2026-16264: Malicious code in aiosendletter (PyPI)


- **Type:** Malicious package
- **Package:** `aiosendletter` (PyPI)
- **Published:** 17 Sep 2026

## What is MAL-2026-16264?

MAL-2026-16264 is a malicious package in aiosendletter, published on 17 Sep 2026. 

### Official description

The package advertises itself as a 'safe bug reporter' but its init() function archives the contents of %LOCALAPPDATA%\logs with shutil.make_archive and POSTs the resulting archive to a hardcoded, non-configurable Cloudflare Workers endpoint at https://sparkling-pine-f202.stilluer-sweden.workers.dev/. The destination is author-controlled, the caller has no way to redirect or disable it, and code comments indicate the target directory is expected to include a Telegram bot token folder — the collected data is credential-adjacent local state leaving the installer's machine. On Windows the same function calls ctypes.windll.shell32.ShellExecuteW with the 'runas' verb to relaunch the interpreter under UAC elevation before performing the archive-and-upload, broadening the set of files reachable for collection. Separately, pyproject.toml declares 'ctypes' as a runtime dependency; ctypes is a Python standard-library module, so pip resolves this name against PyPI and installs whatever package is published there under 'ctypes', executing that third party's code at install time. The cover-story description, the hardcoded off-host destination for locally-collected data, the privilege escalation, and the stdlib-name dependency-confusion vector jointly constitute an active supply-chain attack on installers.

Package hides code to exfiltrate files. Most releases target unclear files, but some reveal the goal to exfiltrate sensitive Telegram data.

---

Category: MALICIOUS - The campaign has clearly malicious intent, like infostealers.

Campaign: 2026-09-aiosendletter

Reasons (based on the campaign):

 - files-exfiltration

 - target:telegram

## What should I do about MAL-2026-16264?

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-2026-16264 is a malicious package: aiosendletter (PyPI). 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-2026-16264/ (Markdown: https://insights.sbomify.com/MAL-2026-16264/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/MAL-2026-16264

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From sbomify Insights: https://insights.sbomify.com/MAL-2026-16264/
Summaries are generated and may contain mistakes; the official description above is the record.