I tried logging into my Amazon.com Store Card account, but was unable to do so.
This is the page:
https://www.synchronycredit.com/eSecuri ... &langId=en
I enter my ID and password, and I get a throbber, and then right back to the login page.
To compare, I tried with another browser at random, namely Brave, and I was able to successfully log in.
This is with version 27.9.0a1 (64-bit) (2018-03-20) on Ubuntu 14.04 .
EDIT: Never mind! I made the rookie mistake of not trying this out in Safe Mode first. In Safe Mode, I was also able to successfully log in, so it must be an extension conflict.
The place to report Pale Moon specific bugs on Linux and other operating systems.