seems you need to update Magento.
http://sitecheck.sucuri.net/results/www.brillen24.be/
http://sitecheck.sucuri.net/results/www.opticien24.fr/

suricata filter give a IDS alert. http://urlquery.net/report.php?id=3646966

Suricata /w Emerging Threats Pro ETPRO WEB_CLIENT Microsoft Internet Explorer remote code execution via option element

if you think avast detection/blocking is wrong, report it here http://www.avast.com/contact-form.php
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