INFOSEC 101: Breaking Down Scary Terms and What They Mean

I am not a hacker. But I understand the information security world. It’s a scary place, unfortunately, to people who have no exposure to it. Yesterday, WordPress 3.0.4 was released as a critical release… and it was. Matt explained the reason for the release in this way:

Version 3.0.4 of WordPress…is a very important update to apply to your sites as soon as possible because it fixes a core security bug in our HTML sanitation library, called KSES. I would rate this release as “critical.”

Simple enough. He goes on to refer to the vulnerability as an XSS vulnerability which caused a bit of angst on Twitter about what that means and if non-technical users should be given more information due to the terminology.

So, as a public service, I give you some basic definitions and concepts of web security and what we mean. These concepts are rightly scary, but the names tend to be scarier to those who don’t understand them.


XSS means cross site scripting. Cross site scripting attacks are generally attacks that occur because something is injected into a URL or “event” on a site to make the site do something else. Do something else can mean “hijack” a site so all visitors are sent somewhere else, or special HTML is injected into a site (often in the form of hidden links that diminish Google search results for the site, etc). This was the nature of the vulnerability fixed in WordPress yesterday.

XSS attacks are almost always carried out because of JavaScript injection. WordPress does have security API that makes dangerous characters (that is, special characters that make JavaScript do things) and it is encouraged that all plugin and theme developers use these APIs. [Docs]


CSRF means Cross Site Request Forgery. With CSRF attacks, browsers (and sometimes other things) are hijacked to “do” things to a website without a user knowing. It’s the proverbial trojan horse where there is an inherent trust from a site that the user/browser is doing something trusted and so attacks riding the coat tails of such trust are given the same trust that the user would also get.

A simple example (does not actually exist) would be that an authenticated user in WordPress with admin privileges is tricked into clicking a link (as the authenticated user) and then admin privileges are transferred to the attacker. We’ve seen this kind of attack on Facebook and Twitter before where DMs or messages are spread across Facebook walls or via Twitter DM).

SQL Injection

SQL Injection is an attack that, without going into the technical details, allows an attacker to send special queries to the database that can alter, modify or even delete a database altogether. You don’t see many of these anymore because most apps are built on frameworks or platforms (like WordPress or Drupal) that have built in routines and APIs that prevent this. In WordPress, there is a prepare() function in the database class which ensures that no SQL injection is possible.

0Day Vulnerabilities

0Day (that is Zero, not “Oh”) is a vulnerability that is exploited before it has been disclosed. Many security researchers work closely with web application developers to alert them to newly discovered vulnerabilities before they are publicly disclosed. They then work with the developers to close the hole before disclosing the vulnerability. The term 0Day comes from the idea that the web app developer knows about the exploit on the 0th day after public disclosure (it hasn’t been disclosed yet).

Denial of Service/(D)DoS

(D)DoS is a (Distributed) Denial of Service attack. These attacks are carried out by flooding a site with traffic/requests to the point where the site can no longer handle the traffic and collapses. If the attack comes from a single source, it’s a DoS but if it comes from more than one, it is a DDoS.

Obviously, there are many aspects of security. We could go way complicated on terminology and concepts, but these are some of the basics you should know when you see something about a vulnerability.

Photo Credit: heathbrandon

Aaron Brazell

Aaron Brazell is a Baltimore, MD-based WordPress developer, a co-founder at WP Engine, WordPress core contributor and author. He wrote the book WordPress Bible and has been publishing on the web since 2000. You can follow him on Twitter, on his personal blog and view his photography at The Aperture Filter.

One thought on “INFOSEC 101: Breaking Down Scary Terms and What They Mean

  1. Thanks for the definitions, could of used this a few months ago when I had an SQL Injection vulnerability with another blogging component I am using, am considering overhauling it now and moving it over to wordpress. Do you know of any way I could migrate from one to another without losing old blog posts?

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