The Web server in 3CX version 15.5.8801.3 is vulnerable to Information Leakage, because of improper error handling in Stack traces, as demonstrated by discovering a full pathname.
The Web server in 3CX version 15.5.8801.3 is vulnerable to Reflected XSS on the api/CallLog TimeZoneName parameter.
The Web server in 3CX version 15.5.8801.3 is vulnerable to Reflected XSS on all stack traces' propertyPath parameters.