skops' Inconsistent Trusted Type Validation Enables Hidden `operator` Methods Execution

skops is a Python library which helps users share and ship their scikit-learn based models. Versions 0.11.0 and below contain a inconsistency in the OperatorFuncNode which can be exploited to hide the execution of untrusted operator methods. This can then be used in a code reuse attack to invoke seemingly safe functions and escalate to arbitrary code execution with minimal and misleading trusted types. This is fixed in version 0.12.0.