Q: AdBlock

there is no need to install it .

AdBlock is safe.

You need to uninstall MacKeeper! It's the worst software around, practically malware itself.

Instructions to remove MacKeeper

https://mackeeper.com/uninstall_mackeeper

For future reference:

Stay away from programs that purport to "clean your Mac". They can do damage to your system. Your Mac needs no cleaning in the first place. All the cleaning that is necessary is taken care routinely by OS X.

There are no viruses that can attack Mac.OS X. So, anti-virus programs are selling a cure for a disease that doesn't exist. And they are renowned for borking Mac systems.

A Mac can pick up malware but not if you just use common sense. You really have to actively invite some malware in for it to happen. That means downloading and knowingly giving your password for it to download. Mac provides all the protection you need with SIP (System Integrity Protection).I About System Integrity Protection on your Mac - Apple Support

If you do happen to download adware you can use MalwareBytes to get rid of it. Malwarebytes was developed by one of our own colleagues here in ASC. It gets rave reviews and is about the most proven anti-malware software for Mac. If you use torrents, don't. Torrents are a good way to pick up malware because anything can hitchhike in on a download.

Safari pop-ups are different and easier to deal with. In Safari 9.1 and later just close the window. For earlier versions force quit and hold the shift key while restarting Safari.

https://support.apple.com/en-us/HT203987

You may have installed ad-injection malware ("adware").

Don't use any kind of "anti-virus" or "anti-malware" product on a Mac. There is never a need for it, and relying on it for protection makes you more vulnerable to attack, not less.

Back up all data first.

If you're not already running the latest version of OS X, updating or upgrading in the App Store may cause the adware to be removed automatically. If you are already running the latest version, please log out or restart the computer. Again, some kinds of malware will be removed—not all. There is no such thing as automatic removal of all possible malware, either by OS X or by third-party software. That's why you can't rely on software to protect you.

If the malware is removed in your case, you'll still need to make changes to the way you use the computer to protect yourself from further attacks. Ask if you need guidance.

If the malware is not removed automatically, see below.

This easy procedure will detect any kind of adware that I know of. Deactivating it is a separate, and even easier, procedure.

Some legitimate software is ad-supported and may display ads in its own windows or in a web browser while it's running. That's not malware and it may not show up. Also, some websites carry intrusive popup ads that may be mistaken for adware.

If none of your web browsers is working well enough to carry out these instructions, restart the computer in safe mode. The malware will be disabled temporarily.

Step 1

Please triple-click the line below on this page to select it, then copy the text to the Clipboard by pressing the key combination command-C:

~/Library/LaunchAgents

In the Finder, select

          Go ▹ Go to Folder...

from the menu bar and paste into the box that opens by pressing command-V. Press return. Either a folder named "LaunchAgents" will open, or you'll get a notice that the folder can't be found. If the folder isn't found, go to the next step.

If the folder does open, press the key combination command-2 to select list view, if it's not already selected. Please don't skip this step.

There should be a column in the Finder window headed Date Modified. Click that heading twice to sort the contents by date with the newest at the top. If necessary, enlarge the window so that all of the contents are showing.

Follow the instructions in this support article under the heading "Take a screenshot of a window." An image file with a name beginning in "Screen Shot" should be saved to the Desktop. Open the screenshot and make sure it's readable. If not, capture a smaller part of the screen showing only what needs to be shown.

Start a reply to this message. Drag the image file into the editing window to upload it. You can also include text in the reply.

Leave the folder open for now.

Step 2

Do as in Step 1 with this line:

/Library/LaunchAgents

The folder that may open will have the same name, but is not the same, as the one in Step 1. As in that step, the folder may not exist.

Step 3

Repeat with this line:

/Library/LaunchDaemons

This time the folder will be named "LaunchDaemons."

Step 4

Open the Safari preferences window and select the Extensions tab. If any extensions are listed, post a screenshot. If there are no extensions, or if you can't launch Safari, skip this step.

Step 5

If you use the Firefox or Chrome browser, open its extension list and do as in Step 4.

If you never rely on strangers who give advice on the Internet, you can't rely on anything you read on this site. None of it comes from Apple. It comes from other end users of Apple products.

yes it's very safe! because if not apple will not allow it with their extension app for safari

MalwareBytes is used by Apple Geniuses at Apple Store Genius Bars, and by Apple Telephone Support agents.

Please search MalwareBytes in Apple Support Discussions and decide for yourself.

Adblock is now an ad-delivery system. Install uBlock instead. See: https://www.ublock.org/

i am not in favour of installing any app , once  some one suggested to install duplicate file finder , it worked but issues start coming in safari , like safari opened after short while , multicoloured spinning beach ball occurred .