One year (or more) ago flash cookies were really a problem, because they could not be deleted from within a browser. They were not managed by the browser but by the flash player. Flash cookies were able to "respawn and recreate" deleted HTTP-cookies.

Is the flash cookie problem nowadays solved? Clearing your cashe and deleting your http cookies within your Chrome, IE, Firefox, etc would also delete flash cookies?

3 Answers 3


As reported here (04/16/2011), it's now easy to delete flash cookies as browser cookies :

The "Flash cookies", also known as local shared objects, can now be deleted through users' browser settings'.

And this, since the v10.3 of Adobe Flash Player. (see the release notes)

  • i also read threatpost.com/en_us/blogs/… but was not sure what the actual status is.
    – Gero
    Commented May 14, 2012 at 9:14
  • I believe it's now sure, but I won't assume this for people using an old flash player (before 10.3).
    – Cyril N.
    Commented May 14, 2012 at 9:20

While "flash cookies" might be easy to clear as cx42net noted above, there are also other techniques that can be used to store hard-to-delete cookie-like data and read it from the server side.

Take a look at evercookie for reference. I've seen this used in relatively high profile e-commerce and content sites.


There are programs that will mitigate the effects of Flash cookies, but there are much more grave threats from using Adobe Flash.

For instance, the zero-day threats include completely taking over your computer.

Here is a website that continually tallies up these threats. Some are cookie based but most are not:


The best approach for normal users is to completely uninstall both Adobe Flash and Adobe Reader and let Chrome handle it for you.

Chrome's code base is constantly being updated to deal with these evolving threats. It will prompt you before playing any Flash content.

There are a lot of other good PDF readers out there, such as Nuance, that do not have the same security holes as Adobe's does.

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