title: Alternative for strict-dynamic in unsupported browsers
body: <p>I have been working on implementing CSP for our web-application and have noticed that on <a href="https://caniuse.com/#search=strict-dynamic" rel="nofollow noreferrer">older browsers</a>, the following error is thrown:</p>
  
  <pre><code>Error] The source list for Content Security Policy directive 'script-src' contains an invalid source: ''strict-dynamic''. It will be ignored.
  </code></pre>
  
  <p>Is there an alternative attribute I can use for browsers that do not yet support this property? Or, should I just remove it?</p>