Something very looking like a big security problem

[Gingko]

Hello.

I registered to FlightRadar24 yesterday.
During registration, I got a confirmation email for validating my account.

There is a thing that I didn't understand :
In the email that I received, the displayed link looked like the following :
https://www.flightradar24.com/premium/confirm/?email=[some personal data]

But the actual link under the text was rather the following :
http://u708499.ct.sendgrid.net/ls/click?upn=[a very large base64 chunk]

This is usually the way that phishing spams try to steal personal data.
But in this case I did want to register.

Is your web site under attack ?
I completed the registration using the displayed link. It seemed to work.
But I worry very much about the reason of this.

Regards,

Gingko

[Oblivian]

If you want an answer, email support. They don't visit forum