TestLink 1.9.20 is vulnerable to Incorrect Access Control in the TestPlan editing section. When a new TestPlan is created, an ID with an incremental value is automatically generated. Using the edit function you can change the tplan_id parameter to another ID. The application does not carry out a check on the user's permissions maing it possible to recover the IDs of all the TestPlans (even the administrative ones) and modify them even with minimal privileges.