Understanding and Stopping URL Redirection Attacks

A URL redirection attack (also called a redirection attack or malicious redirect) takes advantage of users’ trust by secretly sending them from a legitimate website to a malicious page. Cybercriminals often inject hidden redirect code into a site’s files, databases, or .htaccess configuration, or they embed it in phishing emails that imitate trusted brands.

These malicious redirects are more common than many site owners realize. Cyber attacks overall grew by around 30% in mid-2024, and phishing threats, often used to deliver redirects, continue rising across industries.

For example, a cybercriminal might send a phishing email that includes a copycat of your website’s URL. This link might look like your website’s URL, but it is actually a phishing attack that will lead users to a malicious site with forms and login pages that request user credentials and personal information. Because the phishing site link appears legitimate and users believe they’re on a trusted website, they often willingly share personal information without suspicion.

Redirect-based attacks also open the door for other social engineering tactics, such as server-side request forgery (SSRF) and cross-site scripting (XSS), which can further expose sensitive data or grant unauthorized access.

As these threats continue to evolve, understanding how they happen—and how to stop them—is essential for protecting your business, your customers, and your website’s reputation.

What Is a URL Redirection Attack?

A URL redirection attack occurs when a hacker secretly changes a website’s behavior so that visitors are redirected to a different page without consent. Instead of reaching the page they intended to visit, users are sent to a malicious website designed to steal sensitive information, distribute malware, or promote scams.

In most cases, the attacker inserts unauthorized code or modifies redirect functions in the site’s HTML, JavaScript, or .htaccess file. This code then instructs the browser to automatically send visitors to another location, often through an unvalidated redirect or hidden script.

A redirection attack can start from multiple entry points:

• A compromised WordPress plugin or outdated CMS component.
• An injected redirect parameter that tells the browser to load a new URL.
• A phishing email that links to what looks like your legitimate domain but silently routes the user elsewhere.

Because these malicious redirects exploit users’ trust in familiar brands, they’re often used in phishing campaigns that mimic login pages or checkout forms to capture personal details. Some even generate ad revenue by bouncing visitors between multiple sites.

For website owners, these attacks can damage SEO performance, cause blacklisting, and erode customer confidence—making early detection and prevention a top priority.

How Malicious Redirects Work

Malicious redirects typically rely on small changes to code or configuration that cause a site to send visitors to an attacker-controlled destination. Here’s how these redirects most often get created and used in the wild.

1. Injected HTML or JavaScript: Attackers add covert scripts or meta refresh tags to the page source, so a visitor’s browser automatically loads an external URL controlled by the attacker. This can be as simple as a single line of obfuscated JavaScript or a hidden meta tag that triggers a redirect.
2. Compromised plugins and themes: Vulnerable or outdated extensions are a common entry point, allowing hackers to insert redirect code into template files or plugin endpoints that run on page load.
3. Parameter-based redirection: A redirect parameter in a URL, like example.com/redirect?target=..., can be abused when the site blindly trusts that value. Attackers craft links that exploit these parameters to send users to malicious destinations, turning otherwise normal pages into an attack vector.
4. Misused HTTP headers: Some attacks rely on manipulated response headers, for example, when a site returns a Location header pointing to a malicious domain. Attackers can exploit poorly validated redirects by controlling the location header or similar redirect functions.
5. Open redirect attack patterns: Attackers search for pages that act as simple forwarders to other sites, then use those pages inside phishing campaigns so the initial URL looks legitimate while the final destination is harmful.
6. Browser extensions and client-side compromise: Malicious or compromised browser extensions can rewrite page behavior and force redirects locally, which is why attackers sometimes combine server-side and client-side vectors for greater reach.
7. Selective, conditional redirects: Sophisticated campaigns can serve redirects only to certain visitors (for example, users who arrive via search engines), which helps the attack remain stealthy and harder to detect with casual browsing.

Attackers use redirects to harvest credentials on fake login pages, trigger drive-by downloads through malicious links, or funnel traffic to ad-fraud networks that generate revenue for them. These attacks frequently aim to capture sensitive information or install persistent malware that compromises both user data and site integrity.

To reduce risk, website owners should treat redirect handling as a vital part of overall application security. It’s essential to sanitize any user-controlled input, apply strict URL validation, and enforce server-side checks to prevent untrusted destinations from being used in redirects. Regular penetration testing and code reviews can help uncover hidden redirect logic before attackers exploit it. If suspicious redirects are detected, owners should immediately isolate the affected pages, scan for injected files, remove or revert infected code, and apply hardening measures to prevent reinfection.

How to spot a URL redirection vulnerability

Stealthy attacks are difficult to diagnose, including ones that redirect users. Some website owners don’t realize cybercriminals are at work until their web hosts suspend their sites or they notice sudden declines in website traffic, warnings in Google Search Console, or security alerts from automated scanners like SiteLock’s.

Search engines also perform regular site scans and blacklist websites if they detect an infection. However, blacklisting can take time, and your site may remain compromised for days or weeks before you receive a notice, putting visitors and your reputation at serious risk.

The best approach is to monitor your site regularly for signs of a website hacked redirect, or malicious redirects. Look for these key indicators:

• Unexpected drops in organic traffic or engagement.
• Browser warnings or users reporting redirect loops.
• Unfamiliar files or scripts within your site directories.
• Strange search result snippets or spammy URLs under your domain.

There are three common types of redirection vulnerabilities to look out for:

Parameter-Based URL Redirection

Parameter-based URL redirection is a method where the redirection destination is determined by the parameter value in the URL. For instance, a URL like “example.com/redirect?target=maliciousurl.com” would lead users to “maliciousurl.com” if the redirection logic is improperly configured. This technique is stealthy as it uses legitimate web services to redirect users to malicious sites.

To identify parameter-based URL redirection, look out for URLs that include query string parameters like "redirect," "url," "link," "target," and other suggestive terms or parameters that you’re not familiar with on your site. The parameter's value will typically be the destination website. When possible, sanitize user input, enforce URL validation, and limit external redirect parameters to trusted destinations.

Session Restoration URL Redirection

Session Restoration URL Redirection occurs when a user's session state is embedded in the URL to allow the user to bookmark or share their session. For instance, if a user interacts with a dynamic web application and their actions or inputs are saved as URL parameters, this URL can be used to restore the session later. While this is convenient for users, it can be exploited by attackers.

Malicious actors can manipulate the URL parameters to direct users to unintended content or inject malicious scripts after user authentication. This redirection happens when users trust the familiar base domain and may not closely inspect the parameters, making them easy targets.

Watch for unusually long URLs or many parameters to identify Session Restoration URL Redirection. Such URLs are prime candidates for this type of attack, especially if they are generated by web applications that rely heavily on user input.

You should test session-based restoration URLs with a redirect URL appended to it, for example, https://example.com/login?returnUrl=https://www.sitelock.com. Then, ensure validation is applied to verify the URL.

DOM-Based Open Redirects

DOM (Document Object Model) Based URL Redirection is a redirection attack executed in the DOM environment of the victim's web browser. It's different from other types of redirection attacks in that the actual page remains unchanged; instead, the client-side scripts in the page execute differently due to the malicious modifications in the DOM.

For instance, if a web application uses JavaScript to read the document.location property and uses this to decide where to redirect the user; an attacker can manipulate this behavior to take advantage of an open redirection vulnerability that sends users to another site. To reduce this risk, developers should review redirect functions, encode user-supplied data, and validate all inputs before using them within the DOM.

Stay Proactive

Website owners must be proactive regarding their website’s health and security. Regularly scanning your site with a trusted security tool, keeping plugins updated, and reviewing redirect logic in your application code can help you detect issues before they impact your visitors. Cybersecurity solutions like SiteLock can alert you to unvalidated redirects or malicious code the moment they appear, helping you protect your brand and prevent data exposure.

How to stop URL redirection attacks

Fortunately, protecting your website and your customers doesn’t have to be complicated or time-consuming. With a few proactive measures and ongoing monitoring, you can significantly reduce the risk of malicious redirects and open redirect attacks.

Start with these three crucial steps:

1. Use a web application firewall.

A web application firewall is a great first line of defense for directing malicious actors away from your website. Using a WAF guards your site against the most common types of attacks, and some solutions even provide security reports highlighting essential data (such as site traffic). A firewall allows you to monitor your traffic for significant declines, which is also one key sign of a URL redirect attack.

2. Use an automated website scanner.

An automated website scanner will help you detect malware in your site’s files and database faster than if you review them on your own. An effective website scanner should be able to detect and remove these active infections daily to minimize negative impacts on your business and customers. If you suspect your site is redirecting visitors unexpectedly, scan it immediately for malicious code, injected scripts, and hidden files. SiteLock’s automated scanner performs this task continuously to catch new infections in real time.

3. Keep software up-to-date.

Cybercriminals typically gain unauthorized access to small business websites by exploiting outdated code. If you use a content management system, third-party plugins or widgets, or other software to enhance your site, you must be diligent about updating it to avoid open redirect vulnerabilities. Regular updates patch known weaknesses in your website’s codebase, reducing your attack surface. Implement these patches and updates that developers release to fix existing vulnerabilities and mitigate new threats.

4. Check your website code and configuration files.

Sometimes, redirect hacks hide in your website’s code or configuration. Inspect your HTML and JavaScript for any <meta http-equiv="refresh"> tags or suspicious redirect functions. Review your .htaccess file for any unauthorized redirect rules and make sure no strange URLs or IPs have been added. If you’re running WordPress, check for unauthorized admin users, review plugin settings, and verify that your site’s theme files haven’t been modified without approval.

5. Review your hosting and domain settings.

Log in to your hosting control panel or domain registrar and confirm that no unexpected redirects or DNS changes have been added. Attackers sometimes modify domain-level settings to forward traffic elsewhere. Ensuring your DNS, SSL certificates, and redirect parameters are configured properly can prevent persistent hijacks from recurring.

6. Harden your site with ongoing monitoring and mitigation tools.

Even after cleaning a redirect infection, continuous protection is crucial. Automated monitoring, file integrity checks, and penetration testing can reveal recurring redirect attempts before they escalate. SiteLock’s all-in-one website security solution combines malware removal, firewall protection, and automated scanning to ensure that malicious redirects are detected and removed before they can damage your site or reputation.

How to Prevent Future Attacks

Once a redirect vulnerability has been resolved, prevention becomes your most powerful defense. To prevent future issues, focus on reducing your overall attack surface through smart development and security practices.

Sanitize and validate all user inputs to block untrusted redirect parameters and external URLs. Enforce strict URL validation rules within your redirect functions, and use server-side logic instead of relying solely on client-side code. Regular penetration testing and code audits can reveal hidden redirect flaws before attackers do.

Limit access to sensitive information, enforce strong authentication, and keep your CMS and plugins patched. Combining these measures with automated monitoring from a trusted provider like SiteLock ensures ongoing protection and quick mitigation when new threats emerge.

How SiteLock Protects Against URL Redirection Attacks

The cybersecurity landscape is changing rapidly each day, and it can be difficult to keep up with on your own. Having a trusted cybersecurity partner, like SiteLock, who knows how to prevent these attacks, can save you time and keep your customers safe from malicious websites.

SiteLock’s all-in-one protection platform combines automated malware removal, firewall defense, and real-time monitoring to stop URL redirection attacks before they spread. It detects and removes injected code, protects against unvalidated redirects, and provides ongoing remediation and mitigation support to keep your website secure long-term.

Your customers’ trust is vital to the health of your small business. Don’t let cybercriminals take advantage of it. Stay proactive by scanning regularly, validating your redirects, and partnering with SiteLock to secure your site against evolving redirect threats

Safeguard your website today with SiteLock’s website hack cleanup and protection tools. Learn more about SiteLock's website hack cleanup services, and get help today.

Monique Becenti is a product and channel marketing specialist at SiteLock, a cloud-based website security provider currently protecting more than 16 million websites globally. Monique is passionate about improving the customer experience for all. SiteLock’s combination of dedicated research and developmental efforts, aggressive product road maps, and access to a massive global data set make the company a leading innovator in web security.