[Plugin: Fast Secure Contact Form] Form not sending to primary domain addresses

Hi
Although I have domain protection on the form I seem to have been hacked with a spam redirect page actually on my domain so it allows the re-dierct URL? I have since changed the redirect url to # after updating the plugin which has worked for the form and it now redirects correctly, but I’m worried about this spurious URL – where do you think I might find this as it is a copy of my homepage?

https://www.quality-fencing.com/?fp=fLOVgDLvRQIQbRKwwAUVB3SUmQPyXPgRlpO1412S8tPzvjXRawPCifEv2beD0WTqMM4tHx88PAFcEoXSa%2FJnNA%3D%3D&prvtof=2wEm7uhLXXogs9PeE95uhdwDTd3NojtckEOv3p67190%3D&poru=jF%2Fi0TAPnyldjzaXY9oT6%2BTh4sK8LxSSjmbzwc2dwSVRPKiF7NYGB4eB9dZoN3YuIubsTr%2BuWHZqdFTGgAHpBw%3D%3D

this is the html I’m seeing:

<!-- Fast Secure Contact Form plugin 3.1.5.4 - begin - FastSecureContactForm.com -->
<div id="FSContact1" style="width:210px; background-color: #909090;">
<form action="https://www.quality-fencing.com/?fp=fLOVgDLvRQIQbRKwwAUVB3SUmQPyXPgRlpO1412S8tPzvjXRawPCifEv2beD0WTqMM4tHx88PAFcEoXSa%2FJnNA%3D%3D&prvtof=2wEm7uhLXXogs9PeE95uhdwDTd3NojtckEOv3p67190%3D&poru=jF%2Fi0TAPnyldjzaXY9oT6%2BTh4sK8LxSSjmbzwc2dwSVRPKiF7NYGB4eB9dZoN3YuIubsTr%2BuWHZqdFTGgAHpBw%3D%3D#FSContact1" id="si_contact_form1" method="post">
<div style="text-align:left; color:#E8E8E8; padding-top:5px; padding-left:29px; font-size:x-small;">
<span class="required"> *</span>required fields
   </div>

Any help appreciated!