All rankings considered are from the official FIFA's website:
https://inside.fifa.com/fifa-world-ranking/men

In the 2022 World Cup, everyone remembers fondly rooting for the Morocco team (ranked #22 at the time), which unexpectedly reached the semi-finals.

In the 2018 World Cup, Croatia (#20) went all the way to the finals. We also had Russia (#70) and Sweden (#24) reaching quarter-finals.

In the 2014 World Cup, Costa Rica (#28) reached the quarter-finals.

In the 2010 World Cup, Ghana (#32) and Paraguay (#31) reached the quarter-finals

In the 2026 World Cup, will there be a similar dark horse run? Dark horse defined as a team that ranks #17 or below according to the latest FIFA world ranking before the beginning of the world cup reaching at least the quarter finals.

Something to consider is the fact that the world cup format has changed and ranking methodology might have changed as well.

Once we get to the final ranking before the world cup I'll begin adding "Yes and it will be [TEAM]" at your suggestion. Each of these questions will resolve YES if TEAM reaches at least the quarter finals

Once we get to the Round of 16 all remaining dark horse candidates will be added to the market.