I have often heard the remark “WordPress is insecure!”
My response is “Where did you hear that?” and “When did you hear that?”
WordPress Is the Most Popular Content Management System on the Planet.
My first question, “WHERE did you hear that?” is a very important question.
As of this writing, “WordPress powers roughly 18% of the top 10 million websites on the planet, making it the most widely used CMS in the world. The next largest CMS is Joomla, with 3% of the top 10 million sites, and followed by Drupal at 2%.”   
That’s a lot of websites running WordPress! This popularity and widespread usage means that WordPress has a much higher profile than other Content Management Systems (CMS).   A larger install base means a larger target for attackers looking for low-hanging fruit.
The popularity of WordPress brings with it inaccurate or ill-informed attention from journalists and bloggers. Many of those who report on technology matters are not security experts, and often they lack a thorough understanding of the issue. A reporter saying “WordPress is pretty easy to hack” in reference to a scripted brute force attack against weak passwords, does not make it so.
The high profile nature of WordPress solicits the attention of security firms who may have an interest in attracting new customers to a product they offer. By issuing vague security white papers directly to the media, these firms might demonstrate that they are more interested in public relations and “free ink” than actually benefitting the WordPress community.
And just like the “Mac versus PC” debates, and the “Ford versus Chevy” debates, there is often a personal preference involved. A developer may prefer Drupal or SharePoint over WordPress, they may honestly believe that their preferred CMS has a better security model. But without being able to cite specifics, they may rely on the rallying cry “WordPress is insecure!” Just as a Macintosh enthusiast may (incorrectly) say “Windows gets viruses and Macs don’t.”
WordPress Is Secure, You Are Not.
WordPress core is, in fact, very secure, just as secure as any other Content Management System, just as secure as any other software suite or Operating System. Security issues most often arise from administrators and users. In other words, you are the weakest link. A weak password and/or a password used across multiple services, in conjunction with an easily guessable username, is typically the vector of attack against any website. A weak password means a brute force attack script can hammer away on your website until it hits just the right combination to get in, open a back door, add your site to a botnet, lock you out of your site, and potentially infect the computers of your site visitors. This is not a WordPress specific security issue, this is a user issue. If you administer a website, you are an IT professional, own a computer, or have used a computer in the last 20 years, then you should already be aware of the risks of weak passwords. The strategy for preventing exploitation of this attack vector is simple, do not use weak passwords, do not reuse passwords, and do not use easily guessable usernames (like “admin”).
The next likely attack vector is an attack at the file system level of a shared web hosting server. A shared host could be running hundreds of websites on one server. An exploit might not come from an attack directly against your website, but your site can be incidentally compromised if an attack was successful against another site on the same server. The simple solution to this is to use a dedicated or virtual server, avoid shared hosting.
For script kiddies, crackers, and botnet operators, the ever-growing pool of WordPress installs means that there are more sites to check for “low hanging fruit” vulnerabilities. Old versions of software can be compromised because of known vulnerabilities and exploits. The “bad guys” run automated scripts that check what version of a CMS you have, and if they find a version with a known vulnerability, they deploy an exploit and compromise your site. This is not a WordPress specific security issue, this happens with all major software. The solution is to keep your software and all associated add-ons up to date. With WordPress, all it takes is a simple click to keep your installation upgraded.
While it is true that WordPress core is quite stable and secure, security issues can be introduced by third-party software. For instance, a few years ago, there was a widespread attack against websites that implemented the TimThumb image processing script.  Though the TimThumb script is not part of WordPress core, some third-party themes and plugins were using it as an image processor. As a result, an incredible number of websites (estimated in the millions) were compromised, which included non-WordPress sites that had TimThumb installed.  Again, this is not an issue with WordPress core security. This is an issue with third-party software, plugins and themes. The solution to avoid this attack vector is to use themes and plugins listed on WordPress.org. Do not use themes and plugins from untrusted sources.
Historical Legacy and the Current State of WordPress Core Security.
My next question, “WHEN did you hear that?” is an equally important question in response to worry over .
Around 2007–2008, WordPress garnered some unwanted (though admittedly deserved) attention as a number of security issues (in particular SQL injection and code execution vulnerabilities) in WordPress core were exposed.  Of course, these security holes were patched by WordPress developers upon discovery. Those vulnerabilities apply to legacy branches of WordPress and are not present in the most recent WordPress release, 3.6. However, the buzz surrounding those vulnerabilities gave some the feeling that WordPress core was, is, and will forever be insecure.
That is an inaccurate and invalid assessment when it comes to security.
Based on the same criteria, I would argue that your preferred Operating System, software suite, and CMS, was, is, and will forever be insecure. Security breaches and vulnerabilities have been discovered, exploited, and patched in all software. All software is terribly complex, be it an OS, a CMS, or your favorite Word Processor. Due to that complexity, all software suffers from some vulnerabilities (known and unknown) of some kind. All responsible software vendors and developers actively investigate and address vulnerabilities as part of their release cycle. WordPress, Joomla, Drupal, SharePoint, or any other major CMS is no different.
The Real Indication of How Secure a CMS Is, Is Determined by the Vendor’s and Developers’ Response to Security Issues.
For WordPress, the response was to implement an easy “click to update” functionality in WordPress’s Admin Dashboard, a regular release cycle to continually patch and improve core, and a full-time security team to continuously address security issues.
Upgrading WordPress core is easy, it is so “WordPress.” When an administrator with proper privileges accesses the WordPress Dashboard, and an update to WordPress core is available, a simple “WordPress x.x is available! Please update now.” banner displays at the top of the screen. “Update now” is a link to initiate the upgrade process. Additionally, an “Update to x.x” button displays in the “Right Now” metabox. Clicking the “Update” button also initiates the upgrade process. The upgrade process itself consists of clicking a button, waiting a couple of minutes, and you’re done. This makes it easy for a site administrator to keep their installation patched for the latest security fixes. This simplicity is akin to the simplified update systems that the major OS vendors have implemented. Making updates simple means that users are more likely to keep their software patched. And of course keeping software secure means continuously applying security patches.
A regular, ongoing release cycle addresses WordPress core security issues as they are discovered or reported. The release cycle consists of major version upgrades to add features to WordPress, and minor release versions as needed to address security vulnerabilities and critical bugs.  If a critical security vulnerability is identified in core, a security release that addresses the vulnerability is released as quickly as possible (usually within days, sometimes even faster). The number of critical or severe vulnerabilities discovered in WordPress core has decreased significantly since the 2007–2008 years, in part due to the regular release cycle, the simplicity of upgrading, and of course, the security team.
WordPress has a dedicated security team that actively investigates and patches core to address security concerns. This team keeps abreast of all security issues, and enforces security procedures within core. The WordPress security team has a standardized process to address security reports: 
- Receive and acknowledge security report
- Work to confirm the report and its severity
- Plan and develop initial patch to address the security report
- All of this typically happens within 48–72 hours of receiving a security report.
“The WordPress security team is made up of 25 experts including lead developers and security researchers — about half are employees of Automattic, and a number work in the web security field. We consult with well-known and trusted security researchers and hosting companies.” — Andrew Nacin, WordPress Lead Developer, in a presentation “WordPress.org & Optimizing Security for your WordPress sites,” June 2013. 
In conclusion, the vast majority of fear surrounding “WordPress insecurity” is unfounded, and most often is completely unrelated to WordPress core itself. WordPress is secure. What you do with it, how you deploy it, how you administer it, that’s where the real security concerns lay.
Here are some helpful guidelines to keeping your WordPress website safe (for more in-depth security hardening guidelines, visit the Hardening WordPress page in the Codex)
- Use a dedicated or virtual server, avoid shared hosting
- Back up your site (files and database) regularly (consider a service such as VaultPress)
- Keep your WordPress core installation up to date
- Keep your WordPress plugins up to date
- Keep your WordPress themes up to date
- Uninstall (not just disable) any unused plugins or themes
- Avoid plugins and themes from untrusted sources
- Do not use admin (or other easily guessable usernames)
- Use a strong password!
- Ensure your own PC is malware free (to keep keyloggers and malware from stealing your credentials)
- Monitor your server and user stats
- Restrict WP-Admin to your VPN or proxy
- Restrict WP-Admin using HTTP Basic Auth
- Restrict WP-Admin to your IP address
- Deny access to wp-content directories
- Remove WordPress version from meta
- Protect WP-Admin with authentication
- Force SSL
- Get a security audit
- Report potential core vulnerabilities
- Report potential plugin vulnerabilities
If you’re interested in notable WordPress users, there is an ever growing list of government entities, educational institutions, major brands, celebrities, and musicians that rely on WordPress as a secure Content Management System to power their websites and blogs. Visit the WordPress Showcase to see some of the big names that trust WordPress security.