"Chumsearch malware- how to remove from macbook 2015?"
You didn't tell what you use, so my answer is for Safari....
– Open a Finder window. In the Applications folder, look for “MPlayerX”,“NicePlayer”, or other suspicious applications and drag them to the Trash.
– In a Finder window's search field, type "chumsearch", wait a half second, and select "Name matches: chumsearch". Trash any result.
– In Safari, click the Safari menu at top left, choose "Preferences", choose the "Extensions" tab, and remove any items that you don't want.
– In a Finder window, press command shift G.
and then press Return.
– Press command 3 (columns view).
– Scroll down and look for any of these files, and trash them:
FREE ADVICE (and worth every penny)...
– Never agree to any pop-up, even if it appears to be from Adobe.
– Never use any grab-bag site, such as Softonic, Soft32, Softpedia, or CNET. They often do not scan the public submissions before offering them for download.
– To install any Adobe item, start at the actual Adobe site (adobe.com).
– For the options in the Adobe installer about automatic updates, choose "NEVER", because you may agree to a fake malware installer that pretends to be an Adobe update, a very common trick.
– If any installer has a button marked "Custom" or "Advanced" or similar term, click that button to see if it has multiple installers, and select only what you want. Typically, the download would be named "blahblah.mpkg" for a multi-package installer.
Technically, Chumsearch is not malware (mal = bad). It is a search engine extension. This is not the same as a search website.