diff -r be944660c56a -r 3d72ae0968f4 wp/wp-includes/vars.php
--- a/wp/wp-includes/vars.php	Wed Sep 21 18:19:35 2022 +0200
+++ b/wp/wp-includes/vars.php	Tue Sep 27 16:37:53 2022 +0200
@@ -2,8 +2,8 @@
 /**
  * Creates common globals for the rest of WordPress
  *
- * Sets $pagenow global which is the current page. Checks
- * for the browser to set which one is currently being used.
+ * Sets $pagenow global which is the filename of the current screen.
+ * Checks for the browser to set which one is currently being used.
  *
  * Detects which user environment WordPress is being used on.
  * Only attempts to check for Apache, Nginx and IIS -- three web
@@ -29,9 +29,11 @@
 	} else {
 		preg_match( '#/wp-admin/?(.*?)$#i', $_SERVER['PHP_SELF'], $self_matches );
 	}
-	$pagenow = $self_matches[1];
+
+	$pagenow = ! empty( $self_matches[1] ) ? $self_matches[1] : '';
 	$pagenow = trim( $pagenow, '/' );
 	$pagenow = preg_replace( '#\?.*?$#', '', $pagenow );
+
 	if ( '' === $pagenow || 'index' === $pagenow || 'index.php' === $pagenow ) {
 		$pagenow = 'index.php';
 	} else {
@@ -65,7 +67,7 @@
 if ( isset( $_SERVER['HTTP_USER_AGENT'] ) ) {
 	if ( strpos( $_SERVER['HTTP_USER_AGENT'], 'Lynx' ) !== false ) {
 		$is_lynx = true;
-	} elseif ( strpos( $_SERVER['HTTP_USER_AGENT'], 'Edge' ) !== false ) {
+	} elseif ( strpos( $_SERVER['HTTP_USER_AGENT'], 'Edg' ) !== false ) {
 		$is_edge = true;
 	} elseif ( stripos( $_SERVER['HTTP_USER_AGENT'], 'chrome' ) !== false ) {
 		if ( stripos( $_SERVER['HTTP_USER_AGENT'], 'chromeframe' ) !== false ) {