Yes. After the test participant shares their screen, you as the moderator will have the URL the tester is viewing on the bottom of your screen.
*Note: This option only appears after the session has begun, recording has started, and you are actively sharing the participant's screen
At any time, you can change that URL by entering a new URL at the bottom of the Validately session.
On desktop, the test participant needs to click on a button which opens the URL in a new tab.