Aimeos Pagible CMS vulnerable to Server Side Request Forgery (SSRF) via DNS rebinding in admin proxy

In the Aimeos Pagible content management system prior to version 0.10.4, the administrative proxy route (`cmsproxy`) is vulnerable to a Server-Side Request Forgery (SSRF) attack via DNS Rebinding. A Time-of-Check to Time-of-Use (TOCTOU) race condition exists between the URL validation phase and the actual HTTP request phase, allowing attackers to access internal network resources and cloud metadata endpoints. Version 0.10.4 fixes the issue.