With the Java security debacle there are several things that can be learned, mainly the importance of fixing important security bugs sooner by the developers and for users to keep their systems updated.
It also it gives strength to the point that FLOSS software is more secure than its closed sourced counter parts. Being a common good, FLOSS has the advantage that its code is continually check for this kind of security flaws. What's better, it's not only check by the people working for the original developer, but by others from outside can check the code for any vulnerability.
Adding an additional layer of protection, a fix can be offered to the core team of developers by a third party. Meaning that the processes of patching any security hole is speed up, because any security issue can be addresses a lot sooner by anyone who can patch it and sharing that patch with the community at large.
In many ways, there is more people making sure security is as tight as possible. And when a vulnerability is found, a patch can be made available a lot sooner.
Making software safe becomes not the job a small group of coders, but it's the job a all interested in making that software as secure as possible. It becomes harder to exploit any vulnerability, mainly because it goes undetected much less time.
Let's keep in mind that no software will have a perfect security bill, yet FLOSS offers the best way to keep security as tight as possible by having as much eyeballs working to making it as secure as possible.