ZITADEL is an open source identity management platform. From 2.71.11 to before 3.4.10 and 4.15.0, a vulnerability was discovered in Zitadel's LDAP identity provider implementation, which fails to properly escape user-provided usernames before incorporating them into LDAP search filters. This allows unauthenticated attackers to perform LDAP Filter Injection during the login process. While this vulnerability does not allow for a full authentication bypass, an attacker can use LDAP metacharacters (such as *, (, )) to perform blind LDAP injection. By observing the different failure (or success) responses, an attacker can systematically enumerate valid usernames and extract sensitive attribute data from the connected LDAP directory. This vulnerability is fixed in 3.4.10 and 4.15.0.