ci4-cms-erp/ci4ms: System Settings (Mail Settings) Full Platform Compromise & Full Account Takeover for All-Roles & Privilege-Escalation via Stored DOM XSS
Date: 2026-03
Affected: composer/ci4-cms-erp/ci4ms
Attack vector: xss
Category: vulnerability-disclosure
Severity: Critical
CVE: CVE-2026-27599
CWE: CWE-79
CVSS: 9.1 (CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H)

## Summary ### **Vulnerability: Stored DOM XSS via System Settings – Mail Settings (Same-Page Attribute Breakout & Persistent Payload Injection)** - Stored Cross-Site Scripting via Unsanitized Mail Settings Configuration Fields ### Description The application fails to properly sanitize user-controlled input within **System Settings – Mail Settings**. Several configuration fields, including **Mail Server, Mail Port, Email Address, Email Password, Mail Protocol, and TLS settings**, accept attacker-controlled input that is stored server-side and later rendered without proper output encoding. Unlike public-facing XSS that executes on landing pages, this vulnerability executes immediately on the same settings page. The injected payload breaks out of the HTML attribute context and is interpreted by the browser when rendered, resulting in same-page DOM-based XSS. This represents different functionality and a separate vulnerability from landing-page injection. ### Example Affected Fields - Mail Server: `test` - Mail Port: `465` - Email Address: `simple@gmail.com` - Email Password: (any input) - Mail Protocol: `SMTP` - Domain: `simple@domain.com` ### Affected Functionality - System Settings – Mail Settings configuration - Same-page rendering of user-controlled input fields - DOM attribute injection within form inputs - Storage and retrieval of mail configuration values ### Attack Scenario - An attacker injects a malicious JavaScript payload into one or more Mail Settings fields.


Mitigations:

Architectural layers (MAESTRO):