I can't put this any more plainly: If you use Adobe Reader, I urge you to disable its JavaScript support today.A serious security vulnerability has been found in all versions of Adobe's ubiquitous PDF reading software that could allow hackers to run unauthorized code to execute on your computer.

According to a blog post from Adobe's security response team, all currently supported shipping versions of Adobe Reader and Acrobat (Adobe Reader and Acrobat 9.1, 8.1.4, 7.1.1, and earlier versions) are vulnerable.

Yes, that means this advice is for you whether you use Windows, Macintosh, or Unix.

Users are advised to disable JavaScript in Adobe Reader and Acrobat by following these instructions:

1. Launch Acrobat or Adobe Reader. 2. Select Edit/Preferences 3. Select the JavaScript Category 4. Uncheck the 'Enable Acrobat JavaScript' option 5. Click OK

Why most people would ever need JavaScript support inside their PDF readers is another matter entirely. Seems to me like a time bomb that was always waiting to explode.

In my view it would be safer if a wider variety of PDF readers were in use, rather than the vast majority of computer users all relying on Adobe. A list of alternative (and free) PDF readers can be found at pdfreaders.org/

It's not that alternative PDF readers can't have bugs and serious security issues. They can. But at least it would mean a more diverse environment that would make life trickier for the hackers.

Graham Cluley is senior technology consultant at Sophos, and has been working in the computer security field since the early 1990s. When he's not updating his other blog on the Sophos Website, then you can find him on Twitter at @gcluley. Special to Dark Reading.