Even worse in closed source....
Many of the comments here are spot on, but let me throw in a few more:
o It is estimated that .6% of the "PC" base still runs Windows XP, and it is estimated that in one country 60% of their desktop computers runs XP.
o a friend of mine that works for one of those agencies we dare not talk about confirmed that many of the systems we do not want to think about are still running XP.
I mention this not to pick on Microsoft...but if this issue was found to be in XP, how the heck do you fix it?
o What if your closed-source software was written by DEC/SGI/Sun?
Years ago I was involved with a large project to rewrite all the code running on some ancient IBM mainframes at a little facility called the Houston Space Center, in charge of the Shuttle flights. The reason this project was important was that not only had the programmers that wrote the code retired, many of them were dying.
It is relatively easy to bring people back from retirement.
Slide rules typically did not need bug fixes.
This issue is not limited to the FOSS community by a long shot, and actually is easier to correct in FOSS than in closed systems.