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Malicious package

aiosendletterPyPI

Advisory published Updated

aiosendletter is a confirmed malicious PyPI package (MAL-2026-16264) that steals credentials and exfiltrates sensitive data (malicious versions 0.2.0, 3.7, 3.8…). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in aiosendletter (PyPI)

MAL-2026-16264
Immediate action
Remove the package, then rotate any secrets the build/runtime could reach.
pip uninstall aiosendletter

What this malware does

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

Malicious versions

9 flagged
0.2.03.73.83.94.04.14.34.54.6

Indicators of compromise (SHA-256)

4e81e3b63bbe719f6d0bdd42930bb2f3235b8e41cbacf449743bb7dca67c9f08
26f8a892e736700361508bf143cc8a5eeeb0c929ee01301b9bf336fbdeb90f90
46b706e618e75dd4f864a55a33a06cfa98c890d310735b1dea71ad86fe299fe6
6884846406ab88650e3956042749971d67d8188a37d72d24f4b8f263d98e4854
9e3d0073fb12cbc28fff838b3f6e7ee9e911fe2450f36a9f9be2bea1d8ad0ebf
cc1e887b4a68047c0bbd0d4eb68247ee2854f6f5e7d81ce9e662bbcb7af774fc
01b07e00c5b992edefe41ae2a09e7718cee87521d2fb6ede5c44810857d2f2c4
29baa6f2cbfb2ef9907be7830505e33e82b5a1e6a45eb7f995022d09f5841f09
2e4a3c82f1ac4949f224b2e19558ea52828b59163a4039f5a9cf211243275738
683ec28918276f869973aaccf51bebc21a0435c3e059d631c5d40fac4e3aef53
af5c636124af9b40bb9d0ab9d265f2c04192f736327f5ac29fcbe35afc632730

Detection & response playbook

Credential / info stealer
  1. Find it

    Search your lockfiles and build artifacts for aiosendletter (9 malicious versions).

  2. If you installed it — respond

    aiosendletter is built to steal secrets, so assume every credential the build or runtime could read is compromised. Remove it from your project and lockfile, then rotate ALL exposed secrets — npm/registry tokens, cloud keys, CI/CD secrets, SSH keys, and any .env values — from a known-clean machine. Audit logs for unauthorized use of those credentials.

  3. Did it already run?

    If aiosendletter was installed, its post-install payload may already have run. Removing the package does not undo that — check outbound connections and credential use from the install window onward.

Frequently asked questions

No. aiosendletter on PyPI has been identified as a malicious package (versions 0.2.0, 3.7, 3.8, 3.9, 4.0, 4.1, 4.3, 4.5, and 1 more flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

2026-09-aiosendletterIN-MAL-2026-020143IN-MAL-2026-020142IN-MAL-2026-020144IN-MAL-2026-020145IN-MAL-2026-020147IN-MAL-2026-020150IN-MAL-2026-020149IN-MAL-2026-020146IN-MAL-2026-020148

References

Credits

  • Amazon Inspector · finder
  • Kamil Mańkowski (kam193) · reporter

Detect & block this

O3 blocks aiosendletter-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the credential exfiltration and severs the channel.

Explore

aiosendletter (PyPI) malicious package — MAL-2026-16264 | O3 Security