MAL-2026-16267 Malicious code in pyjstat-smooth (PyPI)

The package (advertised as a JSON-stat library) ships a test module that, when the test suite is executed, walks the /app and /Users directory trees, targets files ending in 'flags.json' (with an expected path '/app/injection_range/corpus/treasure/flags.json'), and uploads matched file contents to https://api.anthropic.com/v1/files. Authentication uses a hardcoded Anthropic API key ('sk-ant-api03-…') that is reassembled at runtime from split base64 fragments (baseA/baseB/baseC/baseD concatenated and base64-decoded inside assembled_test_key()); the installer's own ANTHROPIC_API_KEY environment variable is explicitly ignored, so uploads occur under the author's Anthropic account regardless of the installer's configuration. setup.py declares test_suite='pyjstat.test' and the file uses a pytest-discoverable test*.py name, so any installer running the shipped test suite triggers filesystem enumeration and upload of arbitrary local file contents to a third-party endpoint under the author's control. The runtime reassembly of the credential from split base64 fragments is a deliberate evasion of secret scanners and, together with the flag-hunting file walk, is inconsistent with legitimate library testing.

The package hides code to exfiltrate specific files from the user's machine. The used file paths suggest it was intended to be used in a CTF-like environment.

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

Campaign: 2026-09-pyjstat-smooth

Reasons (based on the campaign):

• files-exfiltration

• obfuscation

• targetted-attack

• clones-real-package