Index: wp-includes/media.php
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- wp-includes/media.php	(revision 485984e82e5618c3507666296ea9bb320c153f4c)
+++ wp-includes/media.php	(date 1521012874000)
@@ -927,7 +927,18 @@
 		$html .= ' />';
 	}
 
-	return $html;
+	/**
+	 * Filters the attachment image HTML.
+	 *
+	 * @since 5.0.0
+	 *
+	 * @param string       $html          The attachment image HTML.
+	 * @param int          $attachment_id Image attachment ID.
+	 * @param string       $attr          Attributes for the image markup.
+	 * @param string|array $size          Requested size. Image size or array of width and height values
+	 *                                    (in that order). Default 'thumbnail'.
+	 */
+	return apply_filters( 'attachment_image_html', $html, $attachment_id, $attr, $size );
 }
 
 /**