iPhone/Safari has been hacked

First of all, try to reset your device. This won't delete your data stored on this device.

• Press and hold the Sleep/Wake button
• Press and hold on the Home button
• Keep holding both buttons until the display turns off and back on with Apple logo on it.

Alternatively, you may go to Settings - General - Reset - Reset All Settings

If this does not help, restore your device to factory settings. Note that this will erase the data from your device.

Take a look this Apple Support article: Use iTunes to restore your iPhone, iPad, or iPod to factory settings - Apple Support.

As a final step, try the recovery mode. Turn your device off, then plug it to your computer with the home button pressed. Keep the Home button pressed until you see the iTunes logo on the screen of your device. After that on your computer you should see the iTunes window saying your device needs to be restored to factory settings. Click on the restore button.

More info here:

https://support.apple.com/en-us/HT201263

If these steps don't work, contact Apple and ask for help.

https://www.apple.com/support/iphone/contact/

iPhones cannot catch viruses unless they are jailbroken. They can catch malicious cookies which are easy to remedy. I would reset Safari as suggested below and delete/re-install other browsers to clear their cache.

Close Safari completely from the app switcher window by double clicking the Home button and swiping up the Safari preview pane until it disappears from the screen. Then go to Settings > Safari > Clear History and Website Data. Then do a forced restart. Hold down the Home and Wake/Sleep buttons at the same time for about 15-20 seconds until the Apple logo appears.