My money from my ethereum account were stolen after I acceded the account via MEW CX extension.

Question

The mew cx extension, from google chrom magazine took me to the official site https://www.myetherwallet.com/
I signed  in my account and than I add it in my mew cx extension.
After that I acceseded myetherwallet  account via extension and I saw that all the money from my account were transferred from my
ethereum account without my authorizhation to an unknown address.
The transaction took place at once when adding the mew cx extension.
I don't
understand  what's happened because I used
only chrome extension and the official site.
About this I wrote also to  myetherwallet.com.