<p>I have an HTML page (say welcome.html) which contains an iframe to a page I have no control over (say app.html).  The user performs some actions using the app within the iframe and clicks submit.  Once they do this, they are taken to a new page (say thanks.jsp), which loads within the iframe.  Is there a way in which I can force thanks.jsp to load in the full frame and not the iframe once submit is clicked?  Remember, I have no control over the logic behind that Submit button or app.html.  I do however have control over welcome.html and thanks.jsp.  If possible, I would like to stick with HTML and/or JavaScript.  Thank you in advance.</p>

You probably want to use a framebuster, with a base target in case it fails.
First:
If
```
thanks.jsp
```
is requested via a post request - redirect so it you present the page as the response to a get request.
Then:
Include framebuster JavaScript:
```
```
<script type="text/javascript">
   if (self != top) { top.location.replace(location); }
</script>
```
```
Finally:
In case the user doesn't have JavaScript enabled, make sure they don't stay in the frame any longer then they have to:
```
```
<base target="_top">
```
```