On shut down, popup appears to ask if I want to abort installation

I just found Reset Search and deleted it.

Thanks for your help!

This worked well for me too. It found about 8 adware files and deleted them all. I wasn't able to find and of these things on my own using a variety of methods found here. I WILL be donating to these guys. I am uncertain how this crap gets on my computer, as I'm vigilant with NOT downloading anything I don't want. I find it very curious though that my older computer that is still running Snow Leopard isn't affected by this stuff.

Just to note, much of it is coming from what used to be trusted sites. They're extra installers wrapped around downloads you get from C|NET's download.cnet.com, Softonic.com and others. Even if you notice the little box that gives you the option not to install the "extras", some ignore your choice and install them anyway. If a person wants to be technical about it, they're still trustworthy sites in that adware has yet to be proven dangerous (stealing passwords, back doors, etc.), it's just highly annoying. Though not just annoying, some adware is so invasive and puts so many ads on the screen that the entire Mac slows down.

Illegal downloads are also a really good way to get adware or worse onto your Mac. (Not saying this to you in particular, Sarah. Just noting another common vector).

I had this and followed your advice. Got onto Apple support and set up a chat. I had the Reset search in Launchpad plus a folder called Installmac but the online support agent went through much more and deleted loads of unwanted files and other stuff. The pop up has now gone away for good; thanks again.

I had the same problem, it is an adware. You can install adwaremedic and it will disappears.

This is happening to me as well. My computer is installing stuff without my knowledge, when I go to shut down or restart is says there is an installation in progress do you want to abort?...I'm not downloading anything I'm aware of. I went into activity monitor to see what activity is going on and there are process names going on I don't understand but more importantly there are other users listed under user other than myself for certain processes. Some users are root, _windowserver, _mdnsresponder (65) etc. My friend who has a mac as well only has himself listed as a user on activity monitor. I went to apple preferences then users & groups and I'm listed as the only user for my computer and have always been so these are unauthorized users. I really don't know what to do about it. I'm sure you all probably have the same problem as well, any suggestions?

There's nothing unusual about the other accounts. They all belong to the OS. Some of the items that are running though, do not, and you should get rid of them.

Installer (the one giving you a message with each shutdown) is associated with Genieo adware. You can either follow Apple's manual instructions for removing it, or use the free automated tool, AdwareMedic.

Get rid of the MalwareBytes software. There are no viruses in OS X, so there's nothing to detect. This goes for all AV software. It's all literally useless.

Get rid of Memory Clean. You're fighting against the way Yosemite is designed to work. Unused RAM is wasted RAM, and Yosemite will use as much RAM as it can all the time to keep the computer running faster by using the greatly faster RAM access. Memory Clean is wasting time opening idle RAM when Yosemite is simply going to fill it again.

Went into my launchpad and clicked "Reset Search", I no longer receive the popup asking to abort installation! Thanks a million!!!

This is what worked for me:

http://www.macissues.com/2014/04/23/how-to-detect-and-remove-genieo-for-mac/

download adware medic and install and run it, its free and quick and this is the only real fix thats 100%

adware medic fixes this fast , so down load it and sort that out 100%

Hi,
I know this reply is very late but I had the same problem on shut down and I fixed it..

The problem was a process called AppYs, I found it with the activity monitor
I double clicked the process and opened files and ports and the top line of code was a directory

Library/Application support/quitelex

I went and deleted that location after stopping the AppYs process and shut down.

No more prompt to abort package install

I looked for quitelex and found quitelex.com which is a download manager/ assistant downloader.
However the website is 4 months 3 weeks old so I'm not sure if the software has anything to do with this site or maybe the software was around before any site.
I know that sometimes when you download from certain sites u actually download a download manager that downloads the software for you. (I don't know exactly what a download manager or assistance does since downloading is simple)
I hope I helped someone.

Adwaremedic solved the problem immediately for me.

Quitelex is a variant of the Genieo (aka InstallMac) adware.

I tried the suggestions I saw previously posted. I went to "Finder" and then clicked on applications and looked in each subfolder. I found in my Macinstaller folder that there was an application "reset search." I dragged it into the trash and restarted my computer, now the pop up is gone when I shut down. Really hope this helps because I am not a computer technical person so for me to have been able to find this and get rid of the problem is HUGE for me :-)

Ily