Bugs happen in architecture, aircraft, etc. too. the difference is that the actual engineers are paid to have a precautionary approach -- and spend significant resources -- to actively prevent bugs from making it into the final product.
Amazon and your team has built a great product (I have one and make moderate use of it, have even considered building some skills).
But, you have planted a full-on bugging device in millions of people's homes. Done by a government, this would be cause for war or revolution. This is serious, and you need to treat it much more seriously than you obviously are. Every 'skill' does not require the same minimal levels of security and verification, some, like this one, require much more, or should be forbidden outright until such security can be properly implemented (and yes, this should probably include calls only to pre-configured whitelists, intent confirmation, etc. and to any manager that says "that's too inconvenient to the user", the response is "screw you, it's critical").
You call yourself an "engineer" at least twice, and claim that you take privacy "extremely seriously". The evidence from this incident and others noted in this thread indicates otherwise. Clearly, insufficient resources were allocated to figuring out the potential failure modes of a "call skill", and preventing them.
All due respect, but your team needs more of an engineering approach than you have. This entire "it's gotta ship yesterday" mentality in the software industry used to be just inconvenient. Now it's getting dangerous. Please help stop it.