Description
The character encoding (charset) of this page is dirrectly controlled by user input. The charset can be specified in the Content-Type header or in a meta tag declaration. If an attacker can control the response charset, they could manipulate the HTML to perform XSS or other attacks.
Remediation
It's recommended to force UTF-8 in charset declarations. If the user must control the charset, make sure you are using a whitelist of accepted charsets.
References
Related Vulnerabilities
WordPress Plugin Best WordPress FAQ Cross-Site Scripting (1.4.8)
WordPress Plugin Contact Form Email Cross-Site Scripting (1.1.47)
WordPress Plugin Subscriptions & Memberships for PayPal Cross-Site Scripting (1.1.2)
WordPress Plugin Jetpack-WP Security, Backup, Speed, & Growth Cross-Site Scripting (3.9.1)