Copy Guard is a simple Firefox add-on that warns you when your copy action is hijacked. It compares your selected text with the data added to your clipboard and triggers a notification if there is a difference. It also warns you if your selection contains hidden or offscreen elements. This extension is designed to protect your copy actions and has been reviewed by Mozilla.
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This extension warns you whenever your copy action was hijacked. When you select text and copy it, this extension will compare your selection with the data that was added to your clipboard. If there is a difference, a native notification will be triggered.
Since version 1.1.0 you will receive a warning if your text selection contains hidden or offscreen elements.
IMPORTANT NOTICE: This extension asks for permission to "access your data for all websites". While this may seem invasive, it is required for injecting a script upon loading the page. This script will listen to the copy event and retrieve your current text selection. Please rest assured that no other data is being collected. The source code of this extension has been reviewed by Mozilla and is available on Github.
User reviews
This should be standard in Firefox!
I regularly need to copy scripts from the web, and I am very hesitant to paste sudo commands that might have been altered.
The only reason for a 4-star rating is that it often takes many seconds to show the notification, during which the browser is completely unresponsive.