The RSS Aggregator – RSS Import, News Feeds, Feed to Post, and Autoblogging plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the plugin's 'wp-rss-aggregator' shortcode in all versions up to, and including, 5.0.10 due to insufficient input sanitization and output escaping on user supplied attributes. 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.
https://plugins.trac.wordpress.org/changeset/3439384/wp-rss-aggregator/trunk/core/src/Renderer.php
https://plugins.trac.wordpress.org/browser/wp-rss-aggregator/trunk/core/src/Renderer.php#L209