Concrete CMS (formerly concrete5) below 8.5.10 and between 9.0.0 and 9.1.2 is vulnerable to Reflected XSS - user can cause an administrator to trigger reflected XSS with a url if the targeted administrator is using an old browser that lacks XSS protection. Remediate by updating to Concrete CMS 9.1.3+ or 8.5.10+.