Posting this to old LDAP threads, just as a convenience to Joomla LDAP authentication plugin users:
If you are using the LDAP authentication plugin of Joomla in Joomla 1.5 through 3.7.5: Stop what you are doing and Update immediately to Joomla 3.8.0 (LDAP-security release) !
If you don't understand what LDAP is, then it's not an issue for you (you should sure upgrade to Joomla 3.8, but it's not as urgent).