This script is possibly vulnerable to LDAP Injection attacks.

Lightweight Directory Access Protocol (LDAP) is an open-standard protocol for both querying and manipulating X.500 directory services. When a web application fails to properly sanitize user-supplied input, it is possible for an attacker to alter the construction of an LDAP statement.

When an attacker is able to modify an LDAP statement, the process will run with the same permissions as the component that executed the command. (e.g. Database server, Web application server, Web server, etc.). This can cause serious security problems where the permissions grant the rights to query, modify or remove anything inside the LDAP tree.

Your script should filter metacharacters from user input.

1. See the remedy for solution.
2. If you are not using a database access layer (DAL), consider using one. This will help you centralize the issue. You can also use ORM (object relational mapping). Most of the ORM systems use only parameterized queries and this can solve the whole SQL injection problem.
3. Locate all of the dynamically generated SQL queries and convert them to parameterized queries. (If you decide to use a DAL/ORM, change all legacy code to use these new libraries.)
4. Use your weblogs and application logs to see if there were any previous but undetected attacks to this resource.