Yes, instantly, by any competent anti-cheat. Is it safe from malware? Relatively, because you wrote the code or audited it yourself.
Community measures
Look for feedback from other users. A community that openly discusses issues or updates related to a custom client can be a good sign. hacked eaglercraft client
: ESP (seeing players through walls) and FullBright are the most used, helping players navigate dark caves or track opponents easily. Yes, instantly, by any competent anti-cheat
Several developers maintain repositories of these modified clients, often hosted on platforms like GitHub or CodeSandbox for easy browser access. hacked eaglercraft client