The web browser used within the TikTok app can track every keystroke made by its users, according to new research that is surfacing as the Chinese-owned video app grapples with U.S. lawmakers’ concerns over its data practices. The research from Felix Krause, a privacy researcher and former Google engineer, did not show how TikTok used the capability, which is embedded within the in-app browser that pops up when someone clicks an outside link. But Mr. Krause said the development was concerning because it showed TikTok had built in functionality to…