Redact It от Kyle McLean

This extension lets you redact text and other content from web pages. It can be useful for hiding sensitive information before taking a screenshot of a page.

To redact some text on a web page, select the text and right click, then select "Redact It > Redact Selection".

To redact an entire element, right click on the element, then select "Redact It > Redact Element".

To clear all redactions on the current page, right click on the page, then select "Redact It > Clear Redactions".

You can also redact text selections and clear all redactions by clicking the action button in the add-ons menu. This is currently the only way to interact with the extension on Firefox for Android.