Index: openacs-4/packages/file-storage/www/folder-zip-add.tcl
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/file-storage/www/folder-zip-add.tcl,v
diff -u -r1.11.2.4 -r1.11.2.5
--- openacs-4/packages/file-storage/www/folder-zip-add.tcl	21 Jul 2020 14:06:40 -0000	1.11.2.4
+++ openacs-4/packages/file-storage/www/folder-zip-add.tcl	15 Feb 2021 15:50:05 -0000	1.11.2.5
@@ -108,6 +108,15 @@
 }
 
 # Rest of the form.
+
+# Folder names cannot contain backslashes
+ad_form -extend -name file_add -form {} -validate {
+    {title
+        {[string first "/" $title] == -1}
+        "#acs-templating.Invalid_filename#"
+    }
+}
+
 ad_form -extend -name file_add -form {} -new_data {
     #
     # new_data block, which unzips the file and uploads its contents to the file