CI4MS: Methods Management Full Account Takeover for All-Roles & Privilege-Escalation via Stored DOM XSS
Date: 2026-04
Affected: composer/ci4-cms-erp/ci4ms
Attack vector: xss
Category: vulnerability-disclosure
Severity: Critical
CVE: CVE-2026-34558
CWE: CWE-79
CVSS: 9.1 (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:L)

## Summary ### **Vulnerability: Stored DOM XSS via Methods Management Fields (Global Persistent Payload Execution)** - Stored Cross-Site Scripting via Unsanitized Method Creation and Management Inputs - Automatic Execution Across All Pages Where Method Is Rendered in Navigation ## Description The application fails to properly sanitize user-controlled input within the **Methods Management** functionality when creating or managing application methods/pages. Multiple input fields accept attacker-controlled JavaScript payloads that are stored server-side without sanitization or output encoding. These stored values are later rendered directly into administrative interfaces and global navigation components without proper encoding, resulting in **Stored DOM-Based Cross-Site Scripting (XSS)**. Critically, because created methods are automatically rendered inside the system’s navigation/menu structure, the injected payload executes globally — meaning **every page visited where the malicious method appears in the menu triggers the XSS payload automatically**. This significantly increases severity, as exploitation is not limited to a single view — it becomes a platform-wide persistent execution point. ## Affected Functionality - Methods creation functionality - Methods management and listing functionality - Administrative navigation rendering - Permission-related UI rendering - Global sidebar / menu rendering - Storage and retrieval of method-related data #


Mitigations:

Architectural layers (MAESTRO):