When you install Adblock Plus, you may get a notification that reads something like "This extension can see, read,and change EVERYTHING!!!" Ok.... not that dramatic but the messages can be a bit scary and rightfully so. You should certainly be aware of what extensions can do. Some use this permission for malicious intent. The suite of permissions being requested are simply what is offered by the supported browsers and there is no way for us to request less. Adblock Plus however, only uses the permissions absolutely necessary for ad blocking. I'll get into more details below, you can also check out this article with tips on checking an extensions security Make sure you are installing a Good extension!!!. Note: The article is specific to Chrome but the tips are pretty universal.
To understand this permission, it’s important to know that ad blockers work by first blocking a web page's requests to download ads from the servers that host them, and second, by hiding any ads that can't be blocked.
To do that, the extension needs to:
- See every page you open so that Adblock Plus can work on every page you visit. This also means that Adblock Plus knows the URL of every page you visit.
- See all the data on the page to find any unblocked ads among the other content. This also means that Adblock Plus can see any forms you submit and your browsing activity on that tab.
Granting "Webpage Contents" permission ( Safari) allows ad blockers (like all ad blockers in general) to hide ads if they can't be blocked.