diff --git a/wp-includes/class-wp-image-editor.php b/wp-includes/class-wp-image-editor.php
index a4aa8434d6..11210180b2 100644
--- a/wp-includes/class-wp-image-editor.php
+++ b/wp-includes/class-wp-image-editor.php
@@ -322,6 +322,19 @@ abstract class WP_Image_Editor {
 		 * Enables filtering the mime type used to save images. By default,
 		 * the mapping array is empty, so the mime type matches the source image.
 		 *
+		 * This should be considered experimental as there are a few edge cases that
+		 * still need to be solved.
+		 *
+		 * When this filter is used in combination with the {@see 'wp_editor_set_quality'}
+		 * filter, the image quality value used will be that of the original mime type,
+		 * not the mapped one. This could result in unexpected image quality for generated
+		 * images. See https://core.trac.wordpress.org/ticket/53667 for more details.
+		 *
+		 * When a mime type is mapped to another, and two images with the same name are
+		 * uploaded (image.jpg and image.webp, for example), the generated images for one
+		 * will potentially overwrite the other's.
+		 * See https://core.trac.wordpress.org/ticket/53668 for more details.
+		 *
 		 * @see WP_Image_Editor::get_output_format()
 		 *
 		 * @since 5.8.0
diff --git a/wp-includes/version.php b/wp-includes/version.php
index ad9c6729e3..c5bdfcc271 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.9-alpha-51440';
+$wp_version = '5.9-alpha-51442';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.