Ninja Kiwi uses an anti-cheat system that flags accounts using illegitimate clients. Once flagged (indicated by two green leaves on the settings icon), your account is permanently restricted from leaderboard participation, public co-op matches, and competitive events.
Instead of risking a crack, there are several legitimate ways to access Bloons TD 6 officially: Bloons TD 6 - Ninja Kiwi
Pirated game files are common vectors for Trojans, info-stealers, and keyloggers. These can steal saved browser passwords, cookies, and cryptocurrency wallets.
Many pirated versions come with pre-enabled hacks that trigger automatic bans even if you do not intend to cheat. Official and Safe Ways to Play for Free