The MainSignSearch browser extension is a questionable application that is being spread via deceptive methods. According to infosec researchers, the application was disguised as an installer for a different software program. The reliance on such underhanded methods classifies MainSignSearch as a PUP (Potentially Unwanted Program). Furthermore, once installed on the device, the application may act as adware.
This means that users could be subjected to an annoying influx of unwanted and untrustworthy advertisements. Adware applications often deliver advertisements promoting unsafe destinations - fake giveaways, phishing schemes, technical support frauds, etc. They also could show users advertisements for shady online betting/gaming platforms or adult pages.
PUPs, adware, and browser hijackers could have additional, intrusive functions. Thes applications are notorious for collecting the user data. They may monitor the browsing activities on the device and harvest device details. In some cases, PUPs also have tried to obtain account credentials, banking info, payment numbers, and other, confidential details by accessing browsers' autofill data.