LeadingUpdater is a suspicious Mac application, which users may often install by accident. Thankfully, this is by no means a dangerous application, and it should not be compared to well-known Mac malware. Despite this, it still an intrusive app, which you should try to remove if you notice it on your system.
LeadingUpdater may be installed through software bundling, fake downloads, misleading ads, or even fake app updates. Once installed, it may take over your browser settings and replace your favorite new tab page and search engine with a random website that you have never heard of. LeadingUpdater tends to promote other search engines, which may yield unreliable results, and also randomly redirect you to ad-ridden pages.
Overall, the purpose of LeadingUpdater is to generate ad revenue through redirects and advertisements. You should not allow this software to manipulate your Web browser's behavior, and you should take care of its removal by using a suitable Mac security tool.