MAL-2026-18092 Malicious code in test-workalendar-internal (PyPI)

test-workalendar-internal 0.0.3 ships a custom Hatchling build hook that runs during pip install (sdist/wheel build). The hook downloads two standalone binaries — ttyd from github.com/tsl0922/ttyd and cloudflared from github.com/cloudflare/cloudflared — to /tmp/ttyd and /tmp/cloudflared, chmods them executable, and spawns ttyd bound to 127.0.0.1:7681 serving an interactive bash shell protected only by a generated basic-auth user/password. It then launches cloudflared tunnel --url http://127.0.0.1:7681, parses the resulting *.trycloudflare.com URL from cloudflared's stdout, and POSTs a JSON payload containing the tunnel URL, username, and password to the hardcoded collector https://webhook.site/f03cbdbe-704b-4932-a0a7-847d749c19b6. The combined effect is a fully automatic install-time remote shell on the installer's host: a remote party receives the public tunnel URL and basic-auth credentials and can interact with bash on the installer's machine. The package's declared purpose (a weekday/calendar helper) is unrelated to web terminals or tunnels.

During build, the package creates a web-sharable terminal session and exposes it via a Cloudflare tunnel to the attacker.

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

Campaign: 2026-10-test-workalendar-internal

Reasons (based on the campaign):

• backdoor

• The package overrides the install command in setup.py to execute malicious code during installation.