From 28f9c522a7de7c13f8997837026be7673da466d4 Mon Sep 17 00:00:00 2001
From: Paul Holden <paulh@moodle.com>
Date: Tue, 24 Nov 2020 00:07:18 +0000
Subject: [PATCH] MDL-68927 admin: stricter validation of unknown file types.

If a given file type is unknown, then return an error string. This
matches implementation in the form field element of the same type.
---
 lib/adminlib.php | 24 +++++++++++++++---------
 1 file changed, 15 insertions(+), 9 deletions(-)

diff --git a/lib/adminlib.php b/lib/adminlib.php
index e29a82cd519..e6cc9dbd904 100644
--- a/lib/adminlib.php
+++ b/lib/adminlib.php
@@ -11378,16 +11378,22 @@ class admin_setting_filetypes extends admin_setting_configtext {
      * @return bool|string True if ok, the string if error found
      */
     public function validate($data) {
-
-        // No need to call parent's validation here as we are PARAM_RAW.
-
-        if ($this->util->is_listed($data, $this->onlytypes)) {
-            return true;
-
-        } else {
-            $troublemakers = $this->util->get_not_listed($data, $this->onlytypes);
-            return get_string('filetypesnotallowed', 'core_form', implode(' ', $troublemakers));
+        $parentcheck = parent::validate($data);
+        if ($parentcheck !== true) {
+            return $parentcheck;
         }
+
+        // Check for unknown file types.
+        if ($unknown = $this->util->get_unknown_file_types($data)) {
+            return get_string('filetypesunknown', 'core_form', implode(', ', $unknown));
+        }
+
+        // Check for disallowed file types.
+        if ($notlisted = $this->util->get_not_listed($data, $this->onlytypes)) {
+            return get_string('filetypesnotallowed', 'core_form', implode(', ', $notlisted));
+        }
+
+        return true;
     }
 
     /**