The script (index.php) will get known as two times each time someone visits /confirm/xyz123

Why?

RewriteEngine On
RewriteCond %{REQUEST_FILENAME} -f [NC,OR] 
RewriteCond %{REQUEST_FILENAME} -d [NC] 
RewriteRule .* - [L]

RewriteRule confirm/([a-zA-Z0-9\_\-]+) /confirm/index.php?hashidemail=$1 [L]

Make sure that previous response frontloading-mod-rewrite-rule-is-causing-index-php-to-load-twice.

Test that the request via telnet or wget is actually causeing this to be factor run two times, otherwise this is an empty GEt somewhere inside your previous content.

I believed it. Works out it had been an issue with IIS Mod-Rewrite.

To repair the problem, I simply uninstalled and reinstalled IIS Mod-Rewrite (this time around in ASAPI mode, that is a choice within the setup process).

Hopefully other people who finds themselves with similar problem will discover this publish.

Cheers.