Google is planning to add automated prevention of all downloads initiated from within ad frames which lack user activation. Drive-by-downloads are a technique used by attackers to drop malware payloads on their victims’ computers from compromised websites. The only exception is iOS where Chrome uses iOS WebKit, Apple’s mobile rendering engine and rendering engine. The feature will be available on all platforms except iOS, the only exception being iOS. If a link lives in an ad frame does not have a transient user gesture, the download will be blocked, there will be no user-facing change or alert within Chrome’s user interface.
Source: https://www.bleepingcomputer.com/news/security/google-chrome-to-block-drive-by-downloads-from-ad-frames/