eposta/demo-add-header:v0.2
</code></pre><p>We could then take this <code>FilterDeployment</code> document and version it with the rest of our Istio resources. You may be wondering why we need this Custom Resource to configure Istio&rsquo;s service proxy to use a Wasm extension when Istio already has the <code>EnvoyFilter</code> resource.</p><p>Let&rsquo;s take a look at exactly how all of this works under the covers.</p><h2 id=how-it-works>How it works</h2><p>Under the covers the operator is doing a few th