Index: src/wp-admin/includes/class-wp-plugin-install-list-table.php
===================================================================
--- src/wp-admin/includes/class-wp-plugin-install-list-table.php	(revision 28959)
+++ src/wp-admin/includes/class-wp-plugin-install-list-table.php	(working copy)
@@ -68,7 +68,7 @@
 		switch ( $tab ) {
 			case 'search':
 				$type = isset( $_REQUEST['type'] ) ? wp_unslash( $_REQUEST['type'] ) : 'term';
-				$term = isset( $_REQUEST['s'] ) ? wp_unslash( $_REQUEST['s'] ) : '';
+				$term = isset( $_REQUEST['s'] ) ? wp_unslash( trim( $_REQUEST['s'] ) ) : '';
 
 				switch ( $type ) {
 					case 'tag':