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

Try un-installing and then re-installing.

Adobe Flash Uninstaller

Adobe Flash Player

Adobe Flash Player updates available for OS X on October 24, 2014

A few sites which mention this message point to a compromised router.

Turn your router off, let it sit for about 30 seconds, then turn it back on.

Immediately go into the router's settings by entering either…

192.168.0.1

or

192.168.1.1

…in your web browser. Check the documentation for your router to see what its default IP address is. It should also tell you what the default admin name and passwords are. On many models, that information is also on a sticker on the unit itself.

Find the settings for Remote Management, or something similar. This is how it looks for a CenturyLink DSL modem under the advanced setup.

Note that the top choice for GUI state is Disabled. If yours is enabled, disable it.

I had this problem too, check your launchpad and see if you find an application called "Reset Search", if you do I would recommend going to Apple Support and starting an online chat with an advisor. Even if you don't have the application in your launchpad, I would still recommend starting a chat or making a call to Apple Support, they helped me with this and the pop up no longer appears when I shut down my mac. Good luck!

Thanks dvaidh, I do have an application called 'Reset Search' in my launchpad, so will get onto that chat with Apple Support now.

It was absolutely something to do with that app - a genieo something or other had installed itself all through corners of my mac I wouldn't have known to check. Apple Support online were so helpful and got it all sorted out for me. I'm a happy camper 🙂 Thanks for your help 🙂

I have looked and found that "Reset Search' was in launchpad as well. I just went to 'apps', found it there and binned it. Voila! All good now. Thanks

Cool, glad it helped!!!

I will just clarify though, that it wasn't as simple as binning the app on the launch pad - the Apple Support consultant (online via web chat - free and no questions asked about the fact that my 90days assistance that comes with the Mac has expired - I followed links starting here https://getsupport.apple.com/GetproductgroupList.action) got me to go into all sorts of folders to find it hidden in various places - as well as trashing the icon on the launch pad. I think you would benefit from contacting them if you don't know all the nooks and crannies it can hide 🙂

Had the same problem but none of the above worked. Found the adware culprit with a free anti-virus software app AVIRA... http://www.avira.com/en/free-antivirus-mac

Rather than running an AV software which will most likely cause havoc on your Mac, you could also peruse this site for answers on adware removal and AV testing:

http://www.thesafemac.com/

Personally, I would not recommend running any AV software.

Maybe clarify havoc. Problem was solved in seconds with a quick scan and no havoc detected.

Peruse the site I linked to. He is a regular contributor here and actually downloads viruses, malware, and AV software to test. And, havoc can mean anything but normal system behavior.

I had the same, download a free program called appcleaner, choose applications, select search reset, then delete everything, thats it, gone forever and no dodgy malware installed.

this is the program i used, i was advised by a friend who works for apple.

<Link Edited by Host>

Please do not link to sites which are known to include unwanted additions to software downloads. Downloading from that site is not recommended. The app is available from other sites.

I followed the link as described by 'babowa'.

Against my initial reticence, I went to the http://www.thesafemac.com, read through it and then dowloaded AdwareMedic. Simply, easy. Identified four cases of Genieo adware on my computer, and immediately fixed the pop-up issue on shutdown that has been a consistent problem for me.

This solved my problem. Thank you.

dvaidh's solution worked great for me. The chat support walked me right through what to do, it was amazing how many folders Genieo installed stuff into. Amazing to me at least, as this is the first time I've dealt with something like this.