minor #14187 Add a caution about bind with empty string (jderusse)

This PR was merged into the 4.4 branch.

Discussion
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Add a caution about bind with empty string

Calling `ldap::bind` with a blank password could lead to unexpected behavior.

This PR adds a comment for this

Commits
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539d22d Add a caution about bind with empty string

Author: javiereguiluz

components/ldap.rst

@@ -74,6 +74,10 @@ distinguished name (DN) and the password of a user::
 
     $ldap->bind($dn, $password);
 
+.. caution::
+
+    When the LDAP server allows unauthenticated binds, a blank password will always be valid.
+
 Once bound (or if you enabled anonymous authentication on your
 LDAP server), you may query the LDAP server using the
 :method:`Symfony\\Component\\Ldap\\Ldap::query` method::