Savon::Model generated SOAP operation methods by interpolating operation names into Ruby source passed to module_eval. An attacker who can control the operation names of a WSDL, can inject Ruby code that executes in the application process. This affects only the .all_operations class method provided by Savon::Model to automatically register all operations provided by the WSDL. Configuring Savon::Model with trusted operation names via .operations is safe.

Thanks to @connorshea for securely disclosing this, providing a proof and a great report.