Concrete CMS Stored XSS in the "Next&Previous Nav" block

Concrete CMS versions 9.0.0 to 9.3.4 and below 8.5.19 are vulnerable to Stored XSS in the "Next&Previous Nav" block. A rogue administrator could add a malicious payload by executing it in the browsers of targeted users. Since the "Next&Previous Nav" block output was not sufficiently sanitized, the malicious payload could be executed in the browsers of targeted users.