Embeds: Add the `allow_insecure_embeds` filter.

This allows a site to disable non-SSL embeds.

Fixes #34588.



git-svn-id: https://develop.svn.wordpress.org/trunk@35640 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/class-wp-embed.php

@@ -143,6 +143,18 @@ class WP_Embed {
 			return '';
 		}
 
+		/**
+		 * Optionally allow or block non-SSL embeds.
+		 *
+		 * @since 4.4.0
+		 *
+		 * @param bool   $allowed Flag to determine if non-SSL embeds should be allowed. Default true.
+		 * @param string $url     The URL being embedded.
+		 */
+		if ( 0 !== strpos( $url, 'https://' ) && ! apply_filters( 'allow_insecure_embeds', true, $url ) ) {
+			return false;
+		}
+
 		$rawattr = $attr;
 		$attr = wp_parse_args( $attr, wp_embed_defaults( $url ) );