Poshukach.com appears to be a dubious search engine aimed at Russian-speaking users. However, the fact that it is being promoted via browser hijacker applications means that it can affect users indiscriminately. Affected users will notice that their browser is behaving strangely. Certain settings such as the homepage, new tab page, and the default search engine may be affected and set to open the address of the promoted search engine - Poshukach.com, in this case. Dubious search engines such as Poshukach.com seldomly can deliver meaningful search results. Furthermore, the displayed result list could have numerous sponsored ad links injected into it.
The name of the particular application could vary but users have noticed that a browser extension named mystarttoolbar might be related to the promotion of Poshukach.com. It is important to always pay attention when installing applications from unfamiliar sources. After all, dubious applications such as browser hijackers rely on misleading tactics designed to hide their installation from the user specifically. One such method is called 'bundling.' The PUP (Potentially Unwanted Program) is wrapped inside the installation process of a more popular application, as a preselected choice. Usually, the option is tucked away under the 'Custom' or 'Advanced' settings of the installation.
Browser hijackers and other PUPs are known for having at least some data-harvesting capability. Most are satisfied with capturing the user's browsing activities, such the browsing and search histories. However, some PUPs also may try to obtain sensitive banking or credit/debit card information that has been saved into the affected browser.
Users may try to remove the Poshukach.com engine from their browser manually by reverting each affected setting to its original state. It also may be necessary to remove Poshukach.com from the list of engines associated with the browser. However, some PUPs deploy persistence mechanisms and that may inject the dubious engines they promote right back into the browser, after the next system boot. That is why it is strongly recommended also to scan your system with a professional security product.