Improper Restriction of XML External Entity Reference in ladon

Ladon since 0.6.1 (since ebef0aae48af78c159b6fce81bc6f5e7e0ddb059) is affected by: XML External Entity (XXE). The impact is: Information Disclosure, reading files and reaching internal network endpoints. The component is: SOAP request handlers. For instance: https://bitbucket.org/jakobsg/ladon/src/42944fc012a3a48214791c120ee5619434505067/src/ladon/interfaces/soap.py#lines-688. The attack vector is: Send a specially crafted SOAP call.