"libavcodec may be vulnerable..." message in Firefox

Since last week, I'm receiving the following message for almost every page that I open in Firefox:

libavcodev may be vulnerable or is not supported, and should be updated for play video

Apparently, this is just a warning, 'cause I can play videos normally.

I tried

sudo apt-get install libavcodec

but this package does not exists.

I also did apt-get update and apt-get upgrade, but the message persists.

Finally, when I use apt-get autoremove, it does not return any package.

I googled for the message, but not found anything similar.

What should I do to eliminate this message? Should I stay alert for anything?

Some info:

• Ubuntu 14.04
• Firefox Developer Edition 51.0a2

Solution 1:

There are a security issue described here:

Description

The ff_dwt_decode function in libavcodec/jpeg2000dwt.c in FFmpeg before 2.8.4 does not validate the number of decomposition levels before proceeding with Discrete Wavelet Transform decoding, which allows remote attackers to cause a denial of service (out-of-bounds array access) or possibly have unspecified other impact via crafted JPEG 2000 data.

the libav can be installed through:

sudo apt-get install libav-tools

The libav's version used by ubuntu 14.04 is 9.x and can be upgraded to 11.x as follow :

sudo add-apt-repository ppa:heyarje/libav-11
sudo apt-get update
sudo apt-get install libav-tools

Run:

sudo apt-get update && sudo apt-get upgrade
sudo apt-get dist-upgrade 

to upgrade packages.

Solution 2:

In case you can not upgrade your libav, you can force firefox to use the old version by changing this setting (-> about:config) :

media.libavcodec.allow-obsolete

The defaults setting is false , but you can change it to true .