When 'Disappearing' Messages Don't Disappear 😧
tl;dr 'disappearing' messages may still be stored on your Mac!

blog: "When Disappearing Messages Don't Disappear"
article: "'Disappearing' Signal Messages Stored Indefinitely on Hard Drives"
python script: "dumpNotificationDB.py"

Aloha Patrons! 

On macOS, notifications (those 'alerts' that are shown in the upper top-right corner, when a new iMessage, Slack message, etc, is received), are saved to a system database.  

While this is not shocking news, it's problematic for applications that tout 'disappearing messages' -  such as the popular secure messaging app Signal. Yes, Signal's disappearing messages may end up in this database, even after they have 'disappeared':

Want to see what's in your notification database?
I've just uploaded a simple python script that parses and dumps all notification records 😎

To try out the script:
1) Download "dumpNotificationDB.py"
2) From the terminal (/Applications/Utilities/Terminal.app) run:
   python dumpNotificationDB.py

For more information on all of this - including possible mitigations, read the full blog post: "When Disappearing Messages Don't Disappear"

-patrick