WordPress site owners often focus on plugin and core updates, but the active theme gets less attention. The plugin list is in plain view in the admin. The theme is often something installed years ago and not thought about since. The trouble is that themes are code too. They have the same risks as plugins, and an outdated theme can be just as dangerous as any unpatched plugin sitting on your site.
The security risk
Themes contain PHP. They run on every page load. They include their own functions.php, often with custom helper code that handles forms, AJAX requests, and integrations. Any flaw in that code is reachable from the public web in the same way as a flaw in a plugin.
Common theme vulnerabilities include unauthenticated AJAX endpoints that accept user input without validation, file upload features that lack proper sanitisation, and contact forms or comment handlers that have not been audited for cross site scripting. Premium themes with bundled plugins are also a risk, because the bundled plugin versions are usually pinned and rarely updated when the upstream plugin patches a flaw.
If your theme has not been updated in over a year, treat that as a warning. If it has not been updated in over two years, treat it as effectively abandoned.
The compatibility risk
Themes are designed against a specific WordPress core version, PHP version, and set of associated plugins. As those move forward, an unmaintained theme starts breaking in subtle ways. The block editor renders differently. Modern blocks do not display correctly. PHP warnings appear in the error log. Mobile layouts misbehave on newer browsers. Core Web Vitals scores drop because the theme is generating layout shifts that current browsers measure more strictly.
None of this is dramatic on day one. It is the slow erosion of a site that used to work well.
The performance risk
Old themes commonly load more assets than they need. Multiple jQuery versions. Font Awesome icons even when the site uses only a few of them. Slider libraries from themes that were bought for a specific home page banner and never optimised. These assets show up in every page load and pull Core Web Vitals scores down.
Modern themes built for the block editor are usually leaner, with assets loaded only when the relevant blocks are present on the page. The performance gap between a 2020 theme and a current well built block theme is significant.
The pirated theme problem
A separate risk worth calling out is the practice of downloading premium themes from unofficial sources. A free copy of a hundred dollar theme on a torrent or sharing site is almost always laced with backdoors. The site owner installs the theme, the backdoor activates on first request, and the attacker has full access to the site.
This pattern is depressingly common. The savings on the theme licence cost are a small fraction of the cleanup cost when the inevitable happens. Always buy themes from the official vendor or use the WordPress.org theme repository.
Theme customisation issues
The biggest single mistake we see is direct editing of theme files. A developer makes a change to header.php to fix a layout issue, or adds a function to functions.php to handle something custom. When the theme updates, those changes are wiped.
The right pattern is a child theme. A child theme inherits everything from the parent and lets you override specific files or add specific functions without touching the parent. When the parent updates, your customisations survive.
If your current theme has been edited directly, the right time to fix that is now. Migrate the changes into a child theme. Then you can update the parent safely.
How to assess your theme
Open the theme page in your WordPress admin. Note the theme name, version, author, and the date of the last update. Look up the theme on WordPress.org or the vendor’s site. If the latest version is more than a few minor releases ahead of yours, plan an update. If the last update was over a year ago, plan a migration off it.
Check whether the theme is built for the block editor. Older themes assume the classic editor and feel increasingly clunky in modern WordPress. A block theme is forward compatible with where the platform is going.
Updating a theme safely
The safe pattern is the same as for any significant WordPress change. Backup first. Test on staging. Review the changelog for breaking changes. Update on staging, walk through the site, fix anything that has shifted, then push the change to production during a low traffic window.
For major version updates that include design changes, expect to spend some time adjusting your child theme overrides. For minor updates, it is usually invisible. The discipline is the same. Stage, test, deploy.
When migration is the right answer
Sometimes an old theme is so far behind that updating is more painful than migrating. The original developer is gone, the theme is no longer maintained, the codebase is full of jQuery from another era, and a fresh block theme would give the site a better foundation than continuing to patch the old one.
A planned migration to a current block theme can usually preserve the look and feel of the site while replacing the foundation underneath. The cost is upfront but the savings compound across every future year of maintenance.
Need a hand?
If you would like Smart Coding to audit your WordPress theme, recommend whether to update or migrate, and execute either path safely, get in touch. The theme is the foundation. It is worth getting right.
