title: How to inject JavaScript into an internet forum that parses URLs
body: <p><strong>Hypothetical scenario</strong></p>
  
  <p>There's an interenet forum where typing a regular expression matched as a URL, such as</p>
  
  <pre><code>http://somesite.com
  </code></pre>
  
  <p>will become be made into a link in the HTML of the forum post once it is submitted. So the above link becomes</p>
  
  <pre><code>&lt;a href="http://somesite.com"&gt;http://somesite.com&lt;/a&gt;
  </code></pre>
  
  <p>If possible, I want to exploit this to get JavaScript into the <code>href</code> of the an <code>a</code> tag, i.e. </p>
  
  <pre><code>href="javascript:(function(){alert('Yo, dawg');}())"
  </code></pre>
  
  <p>The key is that I somehow need to get the expression </p>
  
  <pre><code>javascript:(function(){alert('Yo, dawg');}())
  </code></pre>
  
  <p>to do the equivalent, but to be recognized by the parser as a URL. How I can do that? Is there some way of doing it with escape characters, unicode or something else?</p>