Within the past week, give or take, Firefox started blocking the Adobe Shockwave plugin from running in web pages, due to a security problem with it. I could (and did, when I trusted the site) override the warning, but in general bypassing security is a bad idea. Even when the site is trusted, you have to consider the possibility that someone managed to sneak a malicious Flash application onto it.
I was initially happy to upgrade the bugger (to version 18.104.22.1685, which I think is the first one Firefox will allow), but the universe conspired to make that ridiculously difficult. I'm running Linux Mint 16 Petra, which is plumbing-compatible with Ubuntu 13.10 Saucy Salamander. Shockwave is packaged for Ubuntu, not for Mint.
The "Plugins" tab of the Firefox Add-ons Manager flagged Shockwave and gave me a link for updating. That link took me to an Adobe page where I selected which Linux release of the latest version I wanted. I was hoping it would then download a .deb package file, but nooo, it gave me an "APT link", to which I needed to associate an application. Fortunately, I had AptURL installed, so I just had to point to it (in /usr/bin/apturl). Unfortunately, it did not work; I got a message about an unknown channel. So I was stymied there.
The Synaptic package manager was no help; it thought (incorrectly) that the version I had was the most recent. I added the Ubuntu Mozilla Security PPA, which has the latest version, as a source, but I still could not update.
I think I finally figured out what was causing all this wasted effort. As best I can tell, Adobe skipped Ubuntu 13.10 when they released 22.214.171.1245. The version they released for Ubuntu 12.04 (Precise Pangolin) also apparently works on 13.10 ... but the package manager either can't see it or won't use it, because it's for an earlier version of the operating system than what I have. At least I'm guessing that's the problem. The "unknown channel" error I got trying to update via the Adobe site named "Precise" as the channel, so apparently it was looking for the "Precise" version but the package manager wasn't having any of that.
I did eventually succeed, though, and I'll document it here in case any weary pilgrim stumbles on this page. You can find the AMD64 version of the installer package on the Ubuntu packages site. (If you need a different version, backtrack along the bread crumbs -- and good hunting!) The link on that page will download the installer .deb file. Right-click that file, open it with GDebi, click "Install", give the necessary password, and it will download and install the actual Flash player. Restart Firefox and check on the plugins page to verify that you have the up-to-date version.
This was a rather remarkable time-suck compared to most upgrades on Mint or Ubuntu. :-(