From 2edc104c11b13abc2e774d3b89ce33bc4ff28d05 Mon Sep 17 00:00:00 2001
From: Petr Skoda <commits@skodak.org>
Date: Sun, 5 Mar 2023 10:05:57 +0100
Subject: [PATCH] MDL-76688 filter_text: prevent LaTeX3 syntax

---
 filter/tex/lib.php | 1 +
 1 file changed, 1 insertion(+)

diff --git a/filter/tex/lib.php b/filter/tex/lib.php
index 9a0fe3c9c58..3cb8e5cdd27 100644
--- a/filter/tex/lib.php
+++ b/filter/tex/lib.php
@@ -84,6 +84,7 @@ function filter_tex_sanitize_formula(string $texexp): string {
         '\afterassignment', '\expandafter', '\noexpand', '\special',
         '\let', '\futurelet', '\else', '\fi', '\chardef', '\makeatletter', '\afterground',
         '\noexpand', '\line', '\mathcode', '\item', '\section', '\mbox', '\declarerobustcommand',
+        '\ExplSyntaxOn',
     ];
 
     $allowlist = ['inputenc'];