WordPress Form Security: 9 Best Practices for Secure Forms

Adding a form to your site can be incredibly useful. It allows you to collect feedback, enable sign-ups, process orders, or capture leads. The issue is, it also opens up a host of vulnerabilities that bad actors are eager to exploit.

By putting a form on your site, you’re opening up a direct line to your website’s server. This needs to be secured. Many form plugins do include security features to clamp down on form abuse. But there are some extra steps you can and should take to secure your forms.

This article will cover 9 WordPress form security best practices. This way, you can keep spam, malware, and malicious exploits far away from your forms.

Why you need secure WordPress forms

Contact forms are one of the most common ways users interact with your WordPress site. But they’re also a significant entry point for malicious activity.

This can include things like sending spam and phishing emails to your inbox. Or, hijacking your form and using it to send spam to other people. Or, exploiting vulnerabilities through XSS or SQL injection attacks. It’s a risk to you and your website and a risk to your users.

It’s clear, then, why your forms must be secured. While spam may be a manageable annoyance, there are far worse things bad actors can do with your form if left unsecured.

Thankfully, there are plenty of best practices you can implement to make sure your form is secure from any threat.

1. Protect your forms with CAPTCHA

Spam can quickly become a big problem when you put a form on your site. Spambots crawl the web looking for forms and inundate them with waves of unwanted spam and phishing emails, which can drown out legitimate messages sent by your users.

And besides that, many automated programs are coded to scan WordPress sites for forms and attempt to run or upload malicious scripts on your server. If these scripts run successfully, they can potentially compromise your site, leading to unauthorized access or other security issues..

The way to stop all of this in its tracks? CAPTCHA. CAPTCHA is a system for distinguishing between humans and bots, reducing the incidence of spam and other bot-related malicious activities.

While it’s no replacement for securing your SMTP server and sanitizing file upload and input fields, it will stop most automated attacks – especially spam, which can completely overwhelm your inbox without CAPTCHA.

You’ve probably filled out a CAPTCHA before yourself, and it’s a highly effective way to cut down on spam. And our plugin, CAPTCHA 4WP, makes it easy to add this layer of protection to your WordPress forms.

Here’s how CAPTCHA 4WP can help:

• It works with all WordPress forms and is also compatible with plugins like WooCommerce, Gravity Forms, and much more.

• You can use it with most CAPTCHA providers, like Google reCAPTCHA and Cloudflare Turnstile.
• Other security features, like geoblocking, can further lock down your forms.
• You can fully configure how CAPTCHA looks and acts on your site.

If you want to add CAPTCHA to your forms, CAPTCHA 4WP makes it very easy to do. Try the free version or upgrade to premium for more CAPTCHA providers, multi-site licenses, and one-click integrations.

2. Secure file upload fields

File upload fields in your forms can be useful, as they allow people to upload images to help with troubleshooting or submit additional documents. For some sites, allowing file uploads may be necessary.

The issue is, the file upload field can easily be exploited. This can range from an annoyance – people uploading huge files that eat up all your server space – to a serious risk, like uploading a script that compromises your website.

Some things you can do to secure file upload fields:

• Limit the file types that can be uploaded to necessary ones like .png and .jpg. Additionally block known harmful extensions like .exe, .js, and .php.
• Limit the size of files that can be uploaded.
• Set a filename length limit and automatically generate a new file name when it’s uploaded to your server.
• Automatically scan uploaded files for viruses and/or open them in a sandbox application.
• Store uploaded files outside of the web root directory, ideally on a separate server entirely, preventing bad actors from executing scripts.

Overlooking file upload fields can lead to serious security breaches.

3. Sanitize and validate input fields

Input fields on your form, where users type in text, are an easy target for malicious users. They can use these to inject harmful scripts into your website, such as SQL injections or cross-site scripting (XSS) attacks.

All data within input fields must be sanitized (harmful characters that could run malicious scripts are removed or encoded) and validated (fields adhere to certain criteria, like a phone number field containing only numbers and dashes).

That way, even if a user tries to submit malicious code, it will be rendered harmless. Sanitization encodes or escapes special characters that can be used to execute scripts, and validation will prevent them from submitting dangerous data in the first place.

Most form plugins offer built-in options for sanitizing and validating input fields, and it’s worth double-checking these settings. If you’re a developer, you can also write your own code to sanitize and validate inputs.

4. Choose a security-focused form plugin

The foundation of WordPress form security starts with the form plugin you choose. Not all form plugins are created equal – some prioritize features and design, while others put a strong emphasis on security.

It’s best to use a form plugin that comes with built-in security measures and has a strong security track record. While a lot of the work in securing your form is on you, you want to pick a plugin that is actively maintained and doesn’t have a history of exploits going ignored.

Consider plugins like Gravity Forms, which is well-regarded for its security features, including built-in input sanitization and advanced spam protection. CAPTCHA 4WP is another excellent choice, offering features like CAPTCHA and geoblocking to keep your forms secure. And for those needing HIPAA-compliant forms, Jotform provides that level of security, making it ideal for handling sensitive data.

Picking a secure form plugin out of the gate can prevent a lot of headaches in the future, and it gives you a secure foundation to work on.

5. Keep WordPress and form plugins up to date

The fundamental rule of strong website security is keeping everything up to date – that includes the WordPress core, your plugins (most importantly your form plugin), and your theme.

Outdated software is one of the most common entry points for cyberattacks. Once a vulnerability is widely known, it can be easily exploited by anyone. And searching for vulnerable sites doesn’t even need to involve an actual person – bots can be used to scan sites for known vulnerabilities.

When you keep WordPress and your form plugins current, you’re actively reducing the risk of your site being compromised. Developers regularly release updates to patch known vulnerabilities, and failing to install them can leave your site exposed.

No matter how secure a plugin, it can’t have perfect code, and a vulnerability will be discovered eventually. Just as an example, you can find lists of known Gravity Forms vulnerabilities. These have long been patched, but those using older versions of this plugin are still vulnerable.

To avoid such risks, make it a habit to check for updates regularly.

6. Enable TLS (SSL)

TLS, or Transport Layer Security, is the modern standard for securing data transmitted between your website and its visitors. If you’re handling sensitive information like account passwords or payment details, enabling TLS is essential.

Like Secure Sockets Layer (SSL), TLS encrypts the data sent between your visitors and your server, protecting and obfuscating the data so it can’t be easily read. Without encryption, all data submitted through your form is in plain text. In other words, anyone who’s eavesdropping on the connection will see whatever is submitted through the form.

Visually, when TLS (or SSL) is enabled, your site’s URL changes from http:// to https://. Sites without TLS are flagged as “not secure” and can drive away visitors as well.

If you’re running an eCommerce site or collecting any form of personal information, even just email addresses and passwords, TLS is non-negotiable. Sensitive data must be encrypted. Luckily, many hosting providers offer free TLS/SSL certificates.

7. Configure and secure your SMTP server

Along with website hosting, most hosts also bundle in email and/or SMTP hosting. This is how you’re able to send and/or receive emails through your forms.

However, if not properly configured and secured, your SMTP server can become a vulnerable point in your website’s security. Email spoofing, form hijacking, email injection, and data breaches as intruders break into your email system are all risks.

The main thing you can do to secure your email server is encrypting all data that passes between it and your form with TLS or by using end-to-end encryption. You can also implement SMTP authentication so that only authorized users can send email through your server.

WordPress also has SMTP plugins that can help you send emails through an SMTP server once it’s set up and ensure they’re sent using the correct authentication and settings.

8. Go with secure hosting

Another foundational aspect of your site’s security, not just form security, is the web hosting service you choose. Secure hosting is the backbone of a well-protected website and will keep your site isolated, provide a firewall, and scan for any malware that does slip through.

The issue with some forms of hosting, like shared hosting, is that you’re placed on a server with many other websites. Besides potentially opening your site up to vulnerabilities thanks to sharing this server space, it also means you often share an SMTP server. If anyone else on the server sends spam resulting in a blacklist, you’ll be using the same blacklisted server to send out emails.

Good, secure web hosts provide numerous benefits. A firewall can detect and block bots that try to manipulate your forms, and also provide free SSL certificates to encrypt data being sent from them. Plus, a security-focused host provides better servers that are more resilient against malware attacks that can come from forms. And they help keep the server reputation in good standing, which is important all around.

Investing in secure hosting doesn’t have to be expensive either, so it’s a worthwhile investment that can greatly reduce risks.

9. Other ways to stop form abuse

Besides the security measures above, there are several other strategies you can use to cut down on form abuse. Here are a few other ways to protect your forms:

• Honeypots – These are hidden fields in your forms that only bots, not human visitors, can see. If a bot fills out the hidden field, you know the submission is spam.
• Rate limiting – Limit the number of submissions from a single IP address in a certain period, preventing bots from flooding your forms with spam or sending out spam emails.
• Minimum submission time – Bots usually fill out forms instantly, unlike humans who take at least a few seconds. Timing submissions can filter out some bots.
• Geoblocking – Blocking submissions from specific regions causing you issues can help filter out bots.The downside is that this also blocks legitimate users from those regions. CAPTCHA 4WP includes geoblocking features.
• Restrict form access – Instead of making forms public, password-protect them or require users to log in first.

Using these tactics, you can lock down your form effectively.

Strengthening WordPress form security

Securing your WordPress forms is necessary to protect your users, your website, and your data. Forms can be exploited to send annoying spam and run malicious code, so you should take every step you can to protect them.

For an extra layer of protection, we highly recommend our plugin, CAPTCHA 4WP. It’s an effective solution that seamlessly integrates with your forms, blocking bots from sending spam or running scripts. And it works perfectly with most form plugins, WooCommerce, and more, so you can set it up quickly and easily.