WordPress Plugin Login Rebuilder < 2.8.1 - Admin+ Stored XSS
The plugin does not sanitise and escape some of its settings, which could allow high privilege users such as admin to perform Stored Cross-Site Scripting attacks even when the unfiltered_html capability is disallowed (for example in multisite setup).
Login Rebuilder - Fixed in version 2.8.1
Proof of Concept:
1. Go to Settings » Login rebuilder
2. In Login file keyword, add payload: "><iframe src="<svg onload=alert(4);>">
3. Save the changes to trigger XSS.
OWASP top 10 A7: Cross-Site Scripting (XSS)