Screen sharing safety in Waterfox

Screen sharing lets a website receive a live video of a window, browser tab or screen that you select. It can be useful for meetings, co-browsing and remote support, but it can also expose information you did not intend to share.

Share only with a website you trust, and confirm the selected surface before granting permission.

What are the risks?

• A site can record everything visible in the shared area, including notifications, passwords, messages and content that appears after sharing begins.
• Sharing a whole screen can expose other windows when you switch applications or when a notification appears.
• Sharing a browser window can expose tabs or panels that become visible in that window.
• A malicious site can open or reposition content it controls inside the shared area to trick you into revealing private information.

Waterfox warns when a selected sharing surface can include browser content. Stop sharing before opening sensitive pages or stepping away from the computer.

Why screen sharing bypasses normal page isolation

The same-origin policy normally prevents one website from reading another website’s page data. Screen capture does not grant direct access to that data, but it can reveal the pixels displayed by another site. A site receiving the shared video can record those pixels even though its scripts could not otherwise read the page.

For example, if you share an entire screen and then display a signed-in banking page, the receiving site can capture the account details visible on that screen. Closing sensitive tabs, hiding notifications and sharing only the necessary tab or window reduces the risk.

For additional background, see Mozilla’s screen-sharing safety article.

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