One of the joys of working for a government healthcare agency is having to deal with all of the paranoia around dealing with PHI (Protected Health Information). Don\'t get m
The real problem is much deeper than just adding attributes to your HTML - this is common security concern, that's why people invented hardware keys and other crazy things for security.
Imagine you have autocomplete="off" perfectly working in all browsers. Would that help with security? Of course, no. Users will write down their passwords in textbooks, on stickers attached to their monitor where every office visitor can see them, save them to text files on the desktop and so on.
Generally, web application and web developer isn't responsible in any way for end-user security. End-users can protect themselves only. Ideally, they MUST keep all passwords in their head and use password reset functionality (or contact administrator) in case they forgot it. Otherwise there always will be a risk that password can be seen and stolen somehow.
So either you have some crazy security policy with hardware keys (like, some banks offer for Internet-banking which basically employs two-factor authentication) or NO SECURITY basically. Well, this is a bit over exaggerated of course. It's important to understand what are you trying to protect against:
In this particular post, I can see inadequate requirements put on developer which he will never be able to resolve due to the nature of the problem - end-user security. My subjective point is that developer should basically say NO and point on requirement problem rather than wasting time on such tasks, honestly. This does not absolutely make your system more secure, it will rather lead to the cases with stickers on monitors. Unfortunately, some bosses hear only what they want to hear. However, if I was you I would try to explain where the actual problem is coming from, and that autocomplete="off" would not resolve it unless it will force users to keep all their passwords exclusively in their head! Developer on his end cannot protect users completely, users need to know how to use system and at the same time do not expose their sensitive/secure information and this goes far beyond authentication.