Fix escaping in RSS excerpts and descriptions

includes/functions/_setup-wordpress.php

@@ -376,6 +376,24 @@ if ( get_option( 'fictioneer_enable_theme_rss' ) ) {
   add_theme_support( 'automatic-feed-links' );
 }
 
+/**
+ * Ensures RSS excerpts are valid in XML
+ *
+ * @since 5.21.1
+ *
+ * @param string $excerpt  The current post excerpt for the RSS feed.
+ *
+ * @return string The modified excerpt for the RSS feed.
+ */
+
+function fictioneer_filter_rss_excerpt( $excerpt ) {
+  $excerpt = wp_strip_all_tags( $excerpt );
+  $excerpt = esc_html( $excerpt );
+
+  return $excerpt;
+}
+add_filter( 'the_excerpt_rss', 'fictioneer_filter_rss_excerpt' );
+
 // =============================================================================
 // OUTPUT RSS
 // =============================================================================

rss-rss-main.php

@@ -89,7 +89,7 @@ do_action( 'rss_tag_pre', 'rss2' );
   <channel>
 
     <title><?php echo $title; ?></title>
-    <description><?php echo $description; ?></description>
+    <description><![CDATA[<?php echo $description; ?>]]></description>
     <language><?php echo bloginfo_rss( 'language' ); ?></language>
     <atom:link href="<?php self_link(); ?>" rel="self" type="application/rss+xml" />
     <link><?php bloginfo_rss( 'url' ); ?></link>

rss-rss-story.php

@@ -71,7 +71,7 @@ do_action( 'rss_tag_pre', 'rss2' );
   <channel>
 
     <title><?php echo $title; ?></title>
-    <description><?php echo $description; ?></description>
+    <description><![CDATA[<?php echo $description; ?>]]></description>
     <language><?php echo bloginfo_rss( 'language' ); ?></language>
     <atom:link href="<?php self_link(); ?>" rel="self" type="application/rss+xml" />
     <link><?php echo esc_url( get_permalink( $story_id ) ); ?></link>