Index: openacs-4/packages/acs-tcl/tcl/text-html-procs.tcl
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/acs-tcl/tcl/text-html-procs.tcl,v
diff -u -N -r1.109.2.5 -r1.109.2.6
--- openacs-4/packages/acs-tcl/tcl/text-html-procs.tcl	3 Jul 2019 18:12:25 -0000	1.109.2.5
+++ openacs-4/packages/acs-tcl/tcl/text-html-procs.tcl	4 Jul 2019 14:14:25 -0000	1.109.2.6
@@ -879,7 +879,7 @@
                         }
 
                         if { [string tolower $attr_name] ne "style" } {
-                            if { [regexp {^\s*(([^\s:]+):\/\/|(data|javascript))} $attr_value match . p1 p2] } {
+                            if { [regexp {^\s*(([^\s:]+):\/\/|(data|javascript|blob):)} $attr_value match . p1 p2] } {
                                 set protocol [expr {$p1 ne "" ? $p1 : $p2}]
                                 if { ![info exists allowed_protocol([string tolower $protocol])]
                                      && ![info exists allowed_protocol(*)] } {