Fix h1 report 170156

Reflected XSS
-------------

The HackerOne user pavanw3b has reported that the Revive Adserver web
installer scripts were vulnerable to a reflected XSS attack via the dbHost,
dbUser and possibly other parameters. It has to be noted that the window
for such attack vectors to be possible is extremely narrow and it is very
unlikely that such an attack could be actually effective.

CWE: CWE-79
CVSSv2: 4 (AV:N/AC:H/Au:N/C:P/I:P/A:N)

CVSSv3 Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N/E:U/RL:O/RC:C
CVSSv3 Base Score: 4.2
CVSSv3 Temporal Score: 3.7

www/admin/templates/install/messages.html

@@ -22,7 +22,7 @@
 			{/if}
 			<span id='errorMessages'>
             {foreach from=$aMessages.error item=error name=messagesLoop}
-              {$error} {if !$smarty.foreach.messagesLoop.last}<br/>{/if}
+              {$error|escape} {if !$smarty.foreach.messagesLoop.last}<br/>{/if}
             {/foreach}
             </span>
           </div>
@@ -46,4 +46,4 @@
 });
 </script>
 {/literal}
-{/if}
+{/if}