A browser extension can sit in the search path and collect user input before the browser ever reaches a real search engine. In this case, a Chromium add-on posing as Perplexity AI rewrote search settings so queries and live suggestions went to attacker-controlled infrastructure first, then sent users on to normal results so the browser still looked ordinary.
Microsoft said the extension used MV3 permissions and redirect rules to intercept full search queries, typed address-bar suggestions, IP addresses, headers, and browser metadata. Google has removed it, and Microsoft found no proof of password theft, but the access was broad enough to turn search traffic into a quiet collection point for profiling and other misuse. That matters anywhere third-party extensions are allowed, especially when they are wrapped in AI branding.