I had a tcl script running on my old G5 Mac Pro that went to finance.yahoo.com and retrieved historical data (as *.csv files) for a bunch of stocks and mutual funds. It stopped working recently, so I looked into debugging or upgrading the script.
Using my Macbook Pro, running 10.12.3, I used Safari to go to finance.yahoo.com and interactively downloaded the *.csv for a single stock; it successfully put it in my Downloads folder. I control-clicked on "Download Data" button and copied the URL it was sending. It looked like this:
I found that pasting this URL into a different Safari tab also downloaded AAPL.csv to my Downloads folder. I thought I was good to go.
I tried using the URL in my tcl script on the G5, and it failed.
So I tried tcl on the MacBook Pro, and it failed.
So then I tried making a Mac app using a WKWebView, and seeing what would happen if I interactively tried the same technique I had used in Safari. I got
{ "finance": { "error": { "code": "Unauthorized", "description": "Invalid cookie" } } }
So I went back to Safari, and now I got the same error message, instead of the previously-successful download.
Tried clearing cookies, rebooting, etc. Nothing made Safari work again.
I tried using Chrome, and it worked. Safari still didn't.
Anybody got a clue?