SilverStripe through 4.4.x before 4.4.5 and 4.5.x before 4.5.2 allows Reflected XSS on the login form and custom forms. Silverstripe Forms allow malicious HTML or JavaScript to be inserted through non-scalar FormField attributes, which allows performing XSS (Cross-Site Scripting) on some forms built with user input (Request data). This can lead to phishing attempts to obtain a user's credentials or other sensitive user input.

Reflected XSS in SilverStripe