CVE-2026-53906

The vulnerability in MCO is due to missing server-side validation of uploaded file types. Validation relies solely on client-side checks, which can be bypassed. An authenticated, low-privileged attacker can upload files of arbitrary types to the server.

MCO is vulnerable to User Enumeration through authentication-related functionalities. The application returns distinguishable responses for valid and invalid users during username reminder and password reset operations, allowing an attacker to enumerate valid usernames and email addresses.

Stored Cross‑Site Scripting (XSS) vulnerability in MCO allows an attacker to upload a malicious SVG file as the application logo. The JavaScript code executes when the logo is rendered or opened.

A vulnerability in MCO allows an authenticated low-privileged user to retrieve administrator access control structures via the /customer/servlet/mco/webapi/admin-view-hierarchy/get-acl-tree-structure endpoint due to missing authorization checks. This may expose sensitive permission mappings and internal configuration details.

A vulnerability in MCO allows an attacker to lock a victim's account by repeatedly resetting the password. Each reset request invalidates the previous password and temporary passwords, with no limit on the number of resets. An attacker who knows the victim's email and security question answer can effectively deny access to the account.

An IDOR vulnerability in the /customer/servlet/mco/webapi/trading-document/fetchPdfStatement endpoint allows unauthorized access to other users' trading documents. The lack of permission validation enables document retrieval based on a guessable identifier.

A vulnerability in MCO allows an authenticated user to modify group membership without proper authorization checks, leading to privilege escalation. An attacker can add themselves to arbitrary groups by providing a valid group ID, which can be obtained from other application functionalities or guessed via brute-force.