Adobe Flash Plugin is vulnerable/outdated in 14.04 but there is no update in Firefox

I've done some research at mozilla and adobe and tests with both recent LTS-versions (14.04 and 12.04) and I'm pretty sure it is just a numbering problem of the flash-plugin!

To make a long story short:
If you open in firefox "tools" - "add-ons" - "plugins" respectively look at the mozilla check and you've got version 11,2,202,425 (notice the commas!), you will get this error message.
and if your version is 11.2.202.425 (same version, just with dots at the numbering) everything is fine.

So don't panic, your system is safe! ;-)

But I can understand that this message is annoying and so this would be the easiest way to get rid of it:
open a terminal and insert sudo apt-get update && sudo apt-get install -y flashplugin-installer, type your root-password (no characters will be displayed) and just wait till executed!

I would recommend this solution just in the case you have already installed the latest version but still get the error message because of the differences between the flash-packages!

The best solution to the problem of a vulnerable, out-of-date Flash installation--or even an up-to-date one that works poorly--may be to uninstall Flash entirely. Often it is not needed, as HTML5 has largely taken over. Thus removing Flash is a real solution for many people, and should probably be considered first before moving on to other solutions that attempt to keep Flash installed while maintaining it in a current (or semi-current) state.

As occupyflash.org says:

Flash Player is dead. Its time has passed. It's buggy. It crashes a lot. It requires constant security updates. It doesn't work on most mobile devices. It's a fossil, left over from the era of closed standards and unilateral corporate control of web technology. Websites that rely on Flash present a completely inconsistent (and often unusable) experience for fast-growing percentage of the users who don't use a desktop browser. It introduces some scary security and privacy issues by way of Flash cookies.

Flash makes the web less accessible. At this point, it's holding back the web.

Following solution worked for me:

sudo apt-get purge flashplugin-installer
sudo apt-get install adobe-flashplugin

As announced by Adobe Adobe Flash Player 11.2 will be the last version to target Linux as a supported platform.

The main problem in this situation is outdated version of Flash Player in Firefox, which is 11.2
In the same time, Google Chrome users enjoying latest version supported by Google.

The trick is to switch Firefox from using it's Flash Player to Pepper Flash Player from Google Chrome.

1. First of all lets remove that we have:

   sudo apt-get remove flashplugin-installer
   sudo apt-get remove adobe-flashplugin

2. Install Fresh Player Plugin by Rinat Ibragimov.
   It is wrapper which allows Linux users to use Pepper Flash (which is bundled with Google Chrome) in Firefox and other NPAPI-compatible web browsers.
   Latest version at this moment is 0.3.1, and everything seems working.

   sudo add-apt-repository ppa:nilarimogard/webupd8
   sudo apt-get update
   sudo apt-get install freshplayerplugin

3. Install Pepper Flash Player itself from Google Chrome Stable:

   sudo apt-get install pepperflashplugin-nonfree
   sudo update-pepperflashplugin-nonfree --install

   If you want, you can install flash player from different versions:

   Google Chrome Beta:

   sudo update-pepperflashplugin-nonfree --install --beta --unverified

   Google Chrome Unstable:

   sudo update-pepperflashplugin-nonfree --install --unstable --unverified

Now it's time to check version:

1. Adobe About shows that I have 18,0,0,209
2. about:addons shows that I have version 13.1 r2
3. Mozilla's Check Your Plugins page shows that I have version 13.1.2.3, it's outdated and offers update now, but update doesn't work (and we don't need it, actually)

This is not Ubuntu only problem, cause the same message appears in FF on Mageia and openSUSE,

The solution is simple install a plugin for Pepper Flash for Firefox, SUSE team delivered a plugin last week, as soon as problem arised, so that on openSUSES flash is 16.0 like in Chrome

I hope there is a PPA for Ubuntu

http://www.webupd8.org/2014/05/install-fresh-player-plugin-in-ubuntu.html

p.s: the latest 11.2 flash is really outdated(vulnerable), changing version with apt-get wouldn't solve the problem

i currently can't reproduce your error, but this should solve your problem:

open a terminal and insert sudo apt-get update && sudo apt-get install adobe-flashplugin, type your root-password (no characters will be displayed), confirm the dialog and thats it!
well... maybe you have to restart your browser!

1. Access https://get.adobe.com/flashplayer/
2. Choose "Apt for Ubuntu 10.04+" in 'Your system:'
3. Open with Software update application
4. Install..

Forget the steps above ... It will update with an old version of the flash plugin. So it doesn't work. New working steps bellow :)

1. Access https://get.adobe.com/flashplayer/
2. Choose ".tar.gz for other linux"
3. Wait until the download finishes
4. Extract libflashplayer.so in the folder "~/.mozilla/plugins" for your user. For all users you have to extract to /opt/firefox folder (need root permission).

Did this last steps, I don't have these boring messages anymore.

I had this problem on my laptop today, which I had upgraded at some point from Ubuntu 13.10.

It turns out the problem was that the adobe-flashplugin package had no updates, but this was due to the file /etc/apt/sources.list having a reference to saucy still for the partner repository. Editing this file and changing these instances of saucy in the file to trusty as they should have been on upgraded, and then running apt-get update && apt-get upgrade allowed the newer adobe-flashplugin package to get installed.

The following procedure will deactivate the warnings for all plugins, since this error is because of a numbering problem of the flash-plugin as stated by DJCrashdummy you should follow it carefully, maybe reverting the change one month later or so once the flash-plugin get the correct numbering.

1. In your address bar type: about:config
2. Agree to void your warranty
3. Right-click anywhere on the list below and select New > Boolean
4. Copy-paste this phrase into preference name: extensions.blocklist.enabled
5. The variable should be set to false by default, if it isn't on the list, double click it until it is.
6. Reboot the browser

https://support.mozilla.org/en-US/questions/949746