Analysis of malicious telnyx 4.87.1 and 4.87.2 on PyPI — a package with over 1 million monthly downloads: injected code uses WAV audio steganography to deliver payloads that steal credentials and establish persistence. Attributed to TeamPCP.

Two versions of telnyx (4.87.1 and 4.87.2) published to PyPI on March 27, 2026 contain malicious code injected into telnyx/_client.py. The telnyx package averages over 1 million downloads per month (~30,000/day), making this a high-impact supply chain compromise. The payload downloads a second-stage binary hidden inside WAV audio files from a remote server, then either drops a persistent executable on Windows or harvests credentials on Linux/macOS. Stolen data is encrypted with AES-256-CBC and a hardcoded RSA-4096 public key before exfiltration. The RSA key and operational patterns are identical to the litellm PyPI compromise, attributing this attack to TeamPCP with high confidence.

No PyPI trusted publisher (OIDC) is configured. Trusted publishers bind PyPI uploads to a specific GitHub repository and workflow, making stolen tokens useless outside that context. Without this protection, anyone with the API token can upload any version from any machine.

The most likely scenario is that the PYPI_TOKEN was obtained through a prior credential harvesting operation.