An issue was discovered in the Ultimate Member plugin before 2.1.12 for WordPress, aka Unauthenticated Privilege Escalation via User Roles. Due to the lack of filtering on the role parameter that could be supplied during the registration process, an attacker could supply the role parameter with a WordPress capability (or any custom Ultimate Member role) and effectively be granted those privileges.
Multiple Insecure Direct Object Reference vulnerabilities in includes/core/class-files.php in the Ultimate Member plugin through 2.1.2 for WordPress allow remote attackers to change other users' profiles and cover photos via a modified user_id parameter. This is related to ajax_image_upload and ajax_resize_image.
An issue was discovered in the Ultimate Member plugin 2.39 for WordPress. It allows unauthorized profile and cover picture modification. It is possible to modify the profile and cover picture of any user once one is connected. One can also modify the profiles and cover pictures of privileged users. To perform such a modification, one first needs to (for example) intercept an upload-picture request and modify the user_id parameter.
An arbitrary password reset issue was discovered in the Ultimate Member plugin 2.39 for WordPress. It is possible (due to lack of verification and correlation between the reset password key sent by mail and the user_id parameter) to reset the password of another user. One only needs to know the user_id, which is publicly available. One just has to intercept the password modification request and modify user_id. It is possible to modify the passwords for any users or admin WordPress Ultimate Members. This could lead to account compromise and privilege escalation.