Is there any potential risk in doing any transaction or browsing some secure pages inside from a virtual box?
To surf Internet or do risky or whatever actions will just be the same as you are in physical machine, but with respect to the VM itself. But if you are asking if this will affect your host machine then the answer will be NO. whatever you did inside your VM it will not affect your physical host.
Thanks to @kobaltz :
You can still be affected with Viruses that spread aacross networks will just as likely infect the host machine as well as other machines on the network depending on the vNIC settings.