An account-enumeration issue was discovered in Zammad before 3.4.1. The Create User functionality is implemented in a way that would enable an anonymous user to guess valid user email addresses. The application responds differently depending on whether the input supplied was recognized as associated with a valid user.
Source: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-26034
Reference (s):
- https://zammad.com/news/security-advisory-zaa-2020-14