A flaw was found in all python-ecdsa versions before 0.13.3, where it did not correctly verify whether signatures used DER encoding. Without this verification, a malformed signature could be accepted, making the signature malleable. Without proper verification, an attacker could use a malleable signature to create false transactions.
https://pypi.org/project/ecdsa/0.13.3/
https://github.com/warner/python-ecdsa/releases/tag/python-ecdsa-0.13.3