Following my answer. If I can list contents of password-protected ZIP file, check the file types of each stored file and even replace it with another one, without actually knowing the password, then does the ZIP files can be still treated as secure?
This is completely insecure in terms of social engineering / influence etc.
I can hijack (intercept) someone else's file (password-protected ZIP file) and I can replace one of files it contains, with my one (fake, virus) without knowing the password. Replaced file will remain unencrypted, not password-protected inside ZIP, but other files won't be modified.
If victim unpack a password-protected archive, extracting program will ask for the password only once, not every time per each file. So, end user will not see difference -- whether program does not ask for a password, because it already knows it (original file) or because that one doesn't need a password (file modified by me). This way, I can inject something really bad into password-protected ZIP file, without knowing its password and still count on, that receiver will be fouled and assume, file is unmodified.
Am I missing something or this is really wrong? How can we say about something in terms of security, if password is not required to introduce any modifications in password-protected file?