How not to filter untrusted input.

epic_fail_3.java

private InputFilter getCharactersLimited() {
    
    // Limit characters input
    InputFilter[] filters = new InputFilter[1];
    filters[0] = new InputFilter(){
    @Override
    public CharSequence filter(CharSequence source, int start, int end, Spanned dest, int dstart, int dend) {
        if (end > start) {

        char[] acceptedChars = new char[]{'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', 
            'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
            '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', ' ', '(', ')', '-', '{', '}', ':', '\\', '\'', ',', '.', '?', '/', '+'};

        for (int index = start; index < end; index++) {                                         
            if (!new String(acceptedChars).contains(String.valueOf(source.charAt(index)))) { 
            return ""; 
            }               
        }
        }
        return null;
    }

    };
    
    return filters[0];
}