Okay, Let's review:

Ok, lets.

So customer comes to the site, logs in, and currently their information (or more accurately, the location of the file containing the information) is passed via a hidden form field. There's no need for this really. The customer could just be passed a session identifier and all the remaining data would be stored on the server.

I think you are assuming information not in evidence, but basically I agree - and so does Gerard...

This should be a relatively simple switch.

But he doesn't have authority to do it!

That's about equivalent to saying "if he puts locks on the doors and someone breaks in the next day, who's going to take the blame?" It's completely missing the point.

I'd say it closer to: "if he monkies no pun intended) with the alarm system, without authority--and possibly without the skills to know that the monkeying is improving and not worsening the risk--and someone breaks in the next day, who's gonna take the blame?". What point was I missing?

First off, there's no way a cracker's going to be monitoring a web site with these vulnerabilities for weeks and not do anything.

The true crackers, the one's that you never hear about because they do their dirty deeds quietly, without fuss and without leaving traces. They do it for profit not for "fun". The same guys that release script-kiddy tools and how-to tutorials, so that the authorities spend their time chasing the kiddies and not them. They, like any competent thief, don't rush in just because they can, they wait until they are:

1. sure that there is something worth stealing;
2. have all the information they need to gain quick access to what they want;
3. are very sure that their way in and out is clear, quick and safe;
4. they have a reasonable chance of laying a false trail away from them.

It would not be the first time one of these, quiet thieves had sown the seeds of interest in the hAx0r community for a potentially vulnerable site on a relatively open irc channel, then waited for the kiddies to make their play. Whilst they are doing their thing, using well known, clumsy, brute force techniques, the thief sneaks in through a pre-planned backdoor, executes his needs and exits, possibly raising the alarm on the kiddies at the front door on his way out to cover his tracks!

Secondly, not improving the security of a system for fear of being irrationally blamed for future incidents should be cause for dismissal on its own.

First, he has already tried to get authorisation to make the improvements...and was turned down! Hence his question.

Second, there is a very senior monk that made "allegedly unauthorised" changes and have paid the price for his proactive stance and another who had to back off from even giving simple advice for fear of the legal and employment repercussions.