Beego is a popular open-source web framework for the Go programming language. If you’re building web applications in Go, chances are you’ve run across it. But recently, a high-risk Cross-Site Scripting (XSS) vulnerability was discovered in Beego’s RenderForm() function, tracked as CVE-2025-30223. This bug could put your users—and your application—at risk of session hijacking, credential theft, or worse.

Here’s everything you need to know, using clear language, code examples, and links to original sources.

What is CVE-2025-30223?

- CVE-2025-30223 is a critical Cross-Site Scripting (XSS) vulnerability in Beego’s RenderForm() helper.

It affects all Beego versions before 2.3.6.

- The root cause: user-controlled data is rendered into HTML forms without proper escaping—allowing attackers to inject JavaScript code.

Your Go app uses Beego prior to v2.3.6.

- You use the RenderForm() function with any data from users, URLs, or APIs that could be manipulated.

Beego’s RenderForm() is attractive for building forms quickly, but many developers assumed it would properly escape input — like most frameworks do. In this case, it doesn’t.

Explaining the Vulnerability

Beego’s RenderForm() should HTML-escape values placed inside form fields or labels. Instead, it passed user data directly into the output without escaping. Here’s a simplified example:

Suppose you have this handler in your Go app

func showProfileForm(ctx *context.Context) {
    // Assume profile.Name comes from user input somewhere
    form := forms.NewProfileForm(profile) 
    ctx.Output.Body([]byte(RenderForm(form)))
}

If an attacker manages to supply this string as their profile name

"><script>alert('XSS')</script>

They would see the rendered HTML in the browser

<input type="text" name="profile" value="\"><script>alert('XSS')</script>">

The browser treats this as valid markup, executes the JavaScript, and the attacker’s payload runs in your user’s browser.

Stealing cookies, sessions, or impersonating users.

Any place where you use RenderForm() with untrusted data is a possible entry point.

Proof-of-Concept Exploit

Here’s a minimal example showing how an attacker could exploit the vulnerability.

package main

import (
    "github.com/beego/beego/v2/server/web"
    "github.com/beego/beego/v2/client/orm"
    "net/http"
)

func main() {
    web.Router("/", &MainController{})
    web.Run()
}

type MainController struct {
    web.Controller
}

func (c *MainController) Get() {
    // Simulate accepting profile.Name via query parameter
    dangerousName := c.GetString("name")
    formHtml := &lt;form&gt;&lt;input type=&quot;text&quot; name=&quot;profile&quot; value=&quot; + dangerousName + &quot;&gt;&lt;/form&gt;
    c.Ctx.Output.Body([]byte(formHtml))
}

Request this URL in the browser

http://localhost:808/?name="><script>alert('XSSed')</script>;

The browser pops the alert — proof that any injected JavaScript runs!

How Beego Fixed the Flaw

As of Beego v2.3.6 (changelog), RenderForm() now safely escapes all user-supplied values using Go’s built-in html/template escaping system.

Safe code pattern (post-fix)

import "html/template"

func safeFormHandler(ctx *context.Context) {
    unsanitized := ctx.Input.Query("field")
    safeValue := template.HTMLEscapeString(unsanitized)
    formHtml := &lt;form&gt;&lt;input type=&quot;text&quot; name=&quot;profile&quot; value=&quot; + safeValue + &quot;&gt;&lt;/form&gt;
    ctx.Output.Body([]byte(formHtml))
}

But you do not have to sanitize manually if using v2.3.6+. Always upgrade!

Update to v2.3.6 or later immediately!

- Beego 2.3.6 Release Notes

Consider running static analysis for additional XSS vectors.

4. Always sanitize/escape data sent to your templates.

If you can’t upgrade immediately

- Wrap user-provided data in html/template.HTMLEscapeString as a short-term patch.

References and Additional Resources

- Beego 2.3.6 Release Announcement
- GitHub Issue (CVE-2025-30223) *(Refer to official advisories section when updated)*
- OWASP XSS Cheat Sheet
- Go html/template documentation

Conclusion

CVE-2025-30223 is a powerful reminder that form helpers are only as safe as their escaping. If you’re running Beego 2.3.5 or below, upgrade now to protect your users and reputation. Don’t let a simple overlooked bug hand the keys to your castle over to an attacker.

Stay safe, patch early, and always treat user input as hostile.

Timeline

Published on: 03/31/2025 17:15:42 UTC
Last modified on: 04/01/2025 20:26:22 UTC