A DESCRIPTION OF THE PROBLEM :
The compiler doesn't give any error when a class implements a sealed interface which is not listed as permitted,

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
package main;

public class IsThisABug {

    public static void main(String[] args) {
        System.out.println("hello");
    }
}

sealed interface TestInterface permits TestInterface2, TestInterface3 {
}

non-sealed interface TestInterface2 extends TestInterface {
}

sealed interface TestInterface3 extends TestInterface {
}

// allowed to implement sealed interface TestInterface3 even if not permitted?
final class TestClass1 implements TestInterface3 {
}

final class TestClass2 implements TestInterface3 {
}

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
compiler error as TestClass1 and TestClass2 are not permitted to implement TestInterface3
ACTUAL -
prints "hello"

CUSTOMER SUBMITTED WORKAROUND :
add one permitted class (e.g. TestClass1) and it will require the rest to add them to the interface's permit