This practice may be illegal in the USA. Two American companies were sanctioned by the FTC in 2014 for making this same error:
FTC Final Orders with Fandango and Credit Karma Provide Guidance on Mobile App Security
So no HTTPS connections should be possible through the proxy.
Here's the app:
When the app is launched, after clicking through the introductory screens, it invites the user to "Sign in securely" to Amazon:
When the user logs on, the credentials are exposed to the MITM attacker, as shown below.
I got an immediate response from Amazon.
Within 24 hours, I also got a response from the developers of PriceTracker:
Here's the linked article:
Chrome bug triggered errors on websites using Symantec SSL certificates
We had this discussion: