Permissions, Privileges, and Access Controls
files/externallib.php in Moodle through 2.5.9, 2.6.x before 2.6.11, 2.7.x before 2.7.8, and 2.8.x before 2.8.6 does not consider the moodle/user:manageownfiles capability before approving a private-file upload, which allows remote authenticated users to bypass intended file-management restrictions by using web services to perform uploads after this capability has been revoked.
CWE-264 - Permissions Privileges and Access Controls
CWE 264 (permissions, privileges, and access controls) is not a weakness in and of itself, rather it is a category of weaknesses related to the management of permissions, privileges, and other security features used to perform access control. If not addressed, the weaknesses in this category allow attackers to gain privileges for an unintended sphere of control, access sensitive information, and execute arbitrary commands.