diff --git a/src/wp-admin/includes/update.php b/src/wp-admin/includes/update.php
index 5ee195a79f..c514d208e5 100644
--- a/src/wp-admin/includes/update.php
+++ b/src/wp-admin/includes/update.php
@@ -285,7 +285,42 @@ function wp_plugin_update_row( $file, $plugin_data ) {
 		else
 			printf( __('There is a new version of %1$s available. <a href="%2$s" class="thickbox" title="%3$s">View version %4$s details</a> or <a href="%5$s">update now</a>.'), $plugin_name, esc_url($details_url), esc_attr($plugin_name), $r->new_version, wp_nonce_url( self_admin_url('update.php?action=upgrade-plugin&plugin=') . $file, 'upgrade-plugin_' . $file) );
 
-		do_action( "in_plugin_update_message-$file", $plugin_data, $r );
+		/**
+		 * Fires at the end of the update message container in each
+		 * row of the plugins list table.
+		 *
+		 * The dynamic portion of the hook name, $file, refers to the path
+		 * of the plugin's primary file relative to the plugins directory.
+		 *
+		 * @since 2.8.0
+		 *
+		 * @param array $plugin_data {
+		 *     An array of plugin metadata.
+		 *
+		 *     @type string $name         The human-readable name of the plugin.
+		 *     @type string $plugin_uri   Plugin URI.
+		 *     @type string $version      Plugin version.
+		 *     @type string $description  Plugin description.
+		 *     @type string $author       Plugin author.
+		 *     @type string $author_uri   Plugin author URI.
+		 *     @type string $text_domain  Plugin text domain.
+		 *     @type string $domain_path  Relative path to the plugin's .mo file(s).
+		 *     @type bool   $network      Whether the plugin can only be activated network wide.
+		 *     @type string $title        The human-readable title of the plugin.
+		 *     @type string $author_name  Plugin author's name.
+		 *     @type bool   $update       Whether there's an available update. Default null.
+	 	 * }
+	 	 * @param array $r {
+	 	 *     An array of metadata about the available plugin update.
+	 	 *
+	 	 *     @type int    $id           Plugin ID.
+	 	 *     @type string $slug         Plugin slug.
+	 	 *     @type string $new_version  New plugin version.
+	 	 *     @type string $url          Plugin URL.
+	 	 *     @type string $package      Plugin update package URL.
+	 	 * }
+		 */
+		do_action( "in_plugin_update_message-{$file}", $plugin_data, $r );
 
 		echo '</div></td></tr>';
 	}
@@ -342,7 +377,25 @@ function wp_theme_update_row( $theme_key, $theme ) {
 	else
 		printf( __('There is a new version of %1$s available. <a href="%2$s" class="thickbox" title="%3$s">View version %4$s details</a> or <a href="%5$s">update now</a>.'), $theme['Name'], esc_url($details_url), esc_attr($theme['Name']), $r['new_version'], wp_nonce_url( self_admin_url('update.php?action=upgrade-theme&theme=') . $theme_key, 'upgrade-theme_' . $theme_key) );
 
-	do_action( "in_theme_update_message-$theme_key", $theme, $r );
+	/**
+	 * Fires at the end of the update message container in each
+	 * row of the themes list table.
+	 *
+	 * The dynamic portion of the hook name, $theme_key, refers to
+	 * the theme slug as found in the WordPress.org themes repository.
+	 *
+	 * @since 3.1.0
+	 *
+	 * @param WP_Theme $theme The WP_Theme object.
+	 * @param array    $r {
+	 *     An array of metadata about the available theme update.
+	 *
+	 *     @type string $new_version New theme version.
+	 *     @type string $url         Theme URL.
+	 *     @type string $package     Theme update package URL.
+	 * }
+	 */
+	do_action( "in_theme_update_message-{$theme_key}", $theme, $r );
 
 	echo '</div></td></tr>';
 }