How safe is signing in to my Microsoft Account through a third party app?

[Windows Central Question]

I installed a third party calendar on my windows phone from the windows store. It can sync with my Outlook.com account if I sign in to my account. How safe is signing into my account through a third party app from the window store. By the way, the app is Calendar for Business...

 

[ven07]

As far as I can tell, it only needs the connection, so it can read your contacts and appointments, most calendar apps would need that. I'm not saying that I can vouch for the dev, but from the permission list it doesn't seem like he/she is asking for permission for anything out of the ordinary. If you still down trust it create a secondary account, add your contacts to it and try the app out with that one