diff --git a/wp-admin/includes/class-wp-upgrader.php b/wp-admin/includes/class-wp-upgrader.php
index 396672585d..d17a7a7de6 100644
--- a/wp-admin/includes/class-wp-upgrader.php
+++ b/wp-admin/includes/class-wp-upgrader.php
@@ -1025,6 +1025,17 @@ class WP_Upgrader {
 			return false;
 		}
 
+		/**
+		 * Skip any plugin that has "." as its slug.
+		 * A slug of "." will result in a `$src` value ending in a period.
+		 *
+		 * On Windows, this will cause the 'plugins' folder to be moved,
+		 * and will cause a failure when attempting to call `mkdir()`.
+		 */
+		if ( '.' === $args['slug'] ) {
+			return false;
+		}
+
 		$dest_dir = $wp_filesystem->wp_content_dir() . 'upgrade/temp-backup/';
 		// Create the temp-backup directory if it doesn't exist.
 		if ( (
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 5dceb620a3..edf7a35bf8 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.9-beta1-52336';
+$wp_version = '5.9-beta1-52337';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.