diff --git src/wp-admin/includes/dashboard.php src/wp-admin/includes/dashboard.php
index 124dea2206..59232154c5 100644
--- src/wp-admin/includes/dashboard.php
+++ src/wp-admin/includes/dashboard.php
@@ -982,6 +982,20 @@ function wp_dashboard_cached_rss_widget( $widget_id, $callback, $check_urls = ar
 
 	$locale = get_locale();
 	$cache_key = 'dash_' . md5( $widget_id . '_' . $locale );
+
+	/*
+	 * Clear the cached 4.7 w.org feed markup during the upgrade to 4.8.0.
+	 *
+	 * This wasn't done in wp-admin/includes/upgrade.php because that would
+	 * trigger an upgrade screen for users, and it's not worth the UX cost
+	 * for such a small change.
+	 *
+	 * @todo This is a temporary hack for 4.8.0 only, and should be removed in 4.8.1.
+	 */
+	if ( 'dashboard_primary' === $widget_id && false !== strpos( get_transient( $cache_key ), 'rssSummary' ) ) {
+		delete_transient( $cache_key );
+	}
+
 	if ( false !== ( $output = get_transient( $cache_key ) ) ) {
 		echo $output;
 		return true;
diff --git src/wp-admin/includes/upgrade.php src/wp-admin/includes/upgrade.php
index 23a5eee4d7..94ad771761 100644
--- src/wp-admin/includes/upgrade.php
+++ src/wp-admin/includes/upgrade.php
@@ -565,10 +565,6 @@ function upgrade_all() {
 	if ( $wp_current_db_version < 37965 )
 		upgrade_460();
 
-	if ( $wp_current_db_version < 40607 ) {
-		upgrade_480();
-	}
-
 	maybe_disable_link_manager();
 
 	maybe_disable_automattic_widgets();
@@ -1737,26 +1733,6 @@ function upgrade_460() {
 }
 
 /**
- * Executes changes made in WordPress 4.8.0.
- *
- * @ignore
- * @since 4.8.0
- *
- * @global int $wp_current_db_version Current database version.
- */
-function upgrade_480() {
-	global $wp_current_db_version;
-
-	if ( $wp_current_db_version < 40607 ) {
-		// This feature plugin was merged for #40702, so the plugin itself is no longer needed
-		deactivate_plugins( array( 'nearby-wp-events/nearby-wordpress-events.php' ), true );
-
-		// The markup stored in this transient changed for #40702
-		delete_transient( 'dash_' . md5( 'dashboard_primary' . '_' . get_locale() ) );
-	}
-}
-
-/**
  * Executes network-level upgrade routines.
  *
  * @since 3.0.0