[patrickmeenan]

If the proxy is correctly handling the Accept-Encoding (rewriting it with only encodings that it understands), it can either remove the `dcb` and `dcz` encodings or it can check if it knows the announced dictionary and only allow them through if it has the dictionary.

MITM devices that just inspect and fail on unknown content-encoding values will have a problem and will need to be updated (there is an enterprise policy to disable the feature in Chrome for that situation until the proxies can be updated).

[kevincox]

That's a good point. I meant to say proxies that don't alter the headers. These methods could easily be stripped if the proxy wants to ensure that it understands the response.