When an add-on that you have installed triggers the opening of a website that has been reported as a deceptive site (sometimes called a “phishing” page) as a source of unwanted software or as an attack site designed to harm your computer, Firefox will clearly advise you that the site has been blocked for your safety.

When you select See details in the warning message that is displayed you should be able to determine the add-on that is causing this to happen and may wish to disable or remove this add-on. This support article should help Disable or remove Add-ons

The list of malicious websites is maintained by Mozilla to protect users of Firefox. If you are the developer of a legitimate add-on that opens a website that is being blocked in error, please contact Mozilla via your developer hub on https://addons.mozilla.org.

Related content

• Why does Mozilla disable some add-ons from running in Firefox?
• How does built-in Phishing and Malware Protection work?
• Block deceptive content and dangerous downloads in Firefox