Exported HTML5 games are definitely not affected. The Log4j vulnerability is based on Java technology, not to be confused with JavaScript, an entirely different browser-based technology. Therefore HTML5 games use entirely different technologies that are not affected.
The only place Java is used in Construct's exports is for Android apps, and as far as I can tell, the Log4j vulnerability does not affect Android. So in short, it does not affect any of Construct's exports at all.