WordPress Plugin PrePost SEO <= 3.0 - Admin + Stored Cross-Site Scripting
The plugin does not properly sanitize some of its settings, which could allow high-privilege users to perform Stored Cross-Site Scripting (XSS) attacks even when the unfiltered_html capability is disallowed (for example in multisite setup)
PrePost SEO - No known fix - plugin closed
Proof of Concept:
1. Add XSS payload to plugin's "Account API key" setting: "><iframe src="<svg onload=alert(4);>">
2. Save and see XSS exploit.
OWASP top 10 A7: Cross-Site Scripting (XSS)