Because IDM is a popular tool, many third-party sites offer "cracked" versions of the integration module. Malicious versions of idmgcext.crx can: Inject ads into your browsing experience. Track your search history. Steal login credentials.
When you install IDM on your Windows PC, it doesn't automatically "know" when you click a download link in Google Chrome or Microsoft Edge. It needs a bridge. This file is that bridge. Once installed as an extension, it allows IDM to "take over" downloads from the browser, enabling features like: