Index: openacs-4/packages/xowiki/tcl/folder-procs.tcl
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/xowiki/tcl/folder-procs.tcl,v
diff -u -N -r1.55.2.3 -r1.55.2.4
--- openacs-4/packages/xowiki/tcl/folder-procs.tcl	28 Feb 2019 12:50:29 -0000	1.55.2.3
+++ openacs-4/packages/xowiki/tcl/folder-procs.tcl	18 Apr 2019 08:07:54 -0000	1.55.2.4
@@ -668,8 +668,13 @@
     }
 
     lassign [split $orderby ,] att order
-    $t orderby -order [expr {$order eq "asc" ? "increasing" : "decreasing"}] $att
-    set resources_list "[$t asHTML]"
+    if {$att in [$t column_names]} {
+      $t orderby -order [expr {$order eq "asc" ? "increasing" : "decreasing"}] $att
+    } else {
+      ad_log warning "Ignore invalid sorting criterion '$att'"
+      util_user_message -message "Ignore invalid sorting criterion '$att'"
+    }
+    set resources_list [$t asHTML]
 
     if {$menubar ne ""} {
       set mb [::xowiki::MenuBar new -id submenubar]