Improper Restriction of XML External Entity Reference
bw-calendar-engine version contains a XML External Entity (XXE) vulnerability in IscheduleClient XML Parser that can result in Disclosure of confidential data, denial of service, SSRF, port scanning. This attack appear to be exploitable via Man in the Middle or malicious server.
CWE-611 - Improper Restriction of XML External Entity Reference
Listed 4th in the 'OWASP Top Ten', XML External Entities (XXE) vulnerability allows attackers to provide an XML input that contains an external entity. When the XML is parsed, it can cause data extraction and manipulation, execution of commands, denial-of-service attacks, and server-side request forgery.