Pretty sure this is a scam because I opened up my browser and then typed in Yahoos URL and logged into the site, changed my password and security questions, and received an SMS from 619-503-0145 saying that I had just changed my Security Questions. I also notcied that my security questions had not been changed, but I changed them anyways.
I also noticed that when I got the SMS after I changed my SQA, I realized that the part of my SMS that had asterisks in it, was my account name first 2 letters followed by an asterisk. I then looked at the SMS from 732873 and the first 2 letters are not even of my account name.
I strongly advise you do not click on that link in the SMS, nor reply to it because you could probably be verifying your number is active, or the link in the SMS is taki