iFrame <= 4.8 - Authenticated (Contributor+) Stored Cross-Site Scripting via srcdoc

The iFrame plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the srcdoc parameter in versions up to, and including, 4.8 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with contributor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. Since the malicious JS is limited to the scope of the iframe, there is no practical way to steal admin cookies or sessions.