Amazon was notified Aug 28th, 2017
https://www.kb.cert.org/vuls/byvendo...&SearchOrder=4
You will need to contact Amazon about what they are doing and/or what you should do about it.
Kindles where never intended to be a secure platform.
There should not be anything worth having on one of them.
If you do have sensitive material on your Kindle or use your Kindle to communicate sensitive material - The solution is very simple:
Don't do that, just go read a (non-classified) book.