> If Facebook is to make its encrypted chat services interoperable with third parties, it must reserve the right to aggressively fix bugs and patch vulnerabilities. Sometimes, this will make it difficult for competitors to keep up, but protocol security is not something we can afford to sacrifice.

This looks like a barn door, not a loophole. What would stop major players from updating their proprietary protocol on a daily basis? The overhead of staying on top of a dozen big social media sites' protocols would be absurd.

I agree with the need for security, and I see that the industry has failed to update email; but I see that more as a consequence of the industry continually trying to "disrupt" email through the creation of walled gardens.