How the Vulnerability Works
The CVE-2023-28484 vulnerability in Beego stems from improper HTML escaping in the `RenderForm()` function. When generating form fields, user-controlled input is directly embedded into HTML output without sanitization. The `renderFormField()` function constructs HTML strings using `fmt.Sprintf()` with raw user input for attributes like name, value, and label. Since these values aren’t processed with template.HTMLEscapeString(), attackers can inject malicious JavaScript by crafting payloads that break out of HTML attribute contexts. The vulnerability is particularly dangerous because `RenderForm()` returns `template.HTML` type, which tells Go’s templating system to skip automatic escaping. Attackers can exploit this through both attribute injection (e.g., " onmouseover="alert(1)") and direct HTML injection in textarea fields.
DailyCVE Form
Platform: Beego
Version: <2.0.3
Vulnerability: XSS
Severity: High
date: 2023-03-15
What Undercode Say:
// Vulnerable code example
func renderFormField(label, id, class, name, fType string, value interface{}, required bool) template.HTML {
requiredString := ""
if required {
requiredString = " required"
}
return template.HTML(fmt.Sprintf(<code>%v<input%v%v name="%v" type="%v" value="%v"%v></code>,
label, id, class, name, fType, value, requiredString))
}
// Fixed version
func renderFormField(label, id, class, name, fType string, value interface{}, required bool) template.HTML {
requiredString := ""
if required {
requiredString = " required"
}
valueStr := template.HTMLEscapeString(fmt.Sprintf("%v", value))
return template.HTML(fmt.Sprintf(<code>%v<input%v%v name="%q" type="%q" value="%q"%v></code>,
template.HTMLEscapeString(label),
template.HTMLEscapeString(id),
template.HTMLEscapeString(class),
name, fType, valueStr, requiredString))
}
Check if Beego version is vulnerable go list -m github.com/beego/beego | grep -E 'v2.0.[bash]'
<!-- Example attack payload for DisplayName --> <input type="text" name="displayName" value="" onmouseover="alert(1)" data-x=""> <!-- Example attack payload for Bio field --> </textarea><script>alert(document.cookie)</script><textarea>
// Workaround middleware
func XSSProtectMiddleware(ctx context.Context) {
ctx.ResponseWriter.Header().Set("X-XSS-Protection", "1; mode=block")
ctx.ResponseWriter.Header().Set("Content-Security-Policy", "default-src 'self'")
}
Upgrade command go get github.com/beego/beego/[email protected]
// Automated test to verify fix
func TestXSSProtection(t testing.T) {
type TestForm struct {
Field string `form:"xss,text,Label:"`
}
malicious := TestForm{Field: <code>" onload="alert(1)</code>}
output := RenderForm(&malicious)
if strings.Contains(string(output), "onload") {
t.Fatal("XSS vulnerability still exists")
}
}
Nginx mitigation for existing deployments add_header Content-Security-Policy "default-src 'self'"; add_header X-XSS-Protection "1; mode=block";
// Alternative safe form rendering
func SafeRenderForm(obj interface{}) template.HTML {
buf := &bytes.Buffer{}
t := template.New("").Funcs(template.FuncMap{
"safe": func(s string) template.HTML {
return template.HTML(s)
},
})
template.Must(t.Parse(<code>{{define "form"}}...safe template...{{end}}</code>))
if err := t.ExecuteTemplate(buf, "form", obj); err != nil {
return template.HTML("")
}
return template.HTML(buf.String())
}
References:
Reported By: https://github.com/advisories/GHSA-2j42-h78h-q4fg
Extra Source Hub:
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