Overview
In CVE-2026-27131, the Sprig Plugin for Craft CMS allowed admin users and others with explicit access to the Sprig Playground to retrieve the security key, credentials, and other sensitive configuration data, and even to run the hashData() signing function. This real-world exposure demonstrates how insufficient access control can leak secrets when a component exposes sensitive fields through a UI or API. The mitigation disabled the Sprig Playground when devMode is off by default and added a flag enablePlaygroundWhenDevModeDisabled to opt-in; this highlights the importance of restricting exposure by default and using explicit enablement flags for dangerous features. This vulnerability class maps to Broken Object Property Level Authorization when an API returns object properties without enforcing per-field access rules, enabling unauthorized actors to access sensitive data.
In Go with Gin, a similar pattern appears when a handler returns a struct that contains secrets (for example SSN, credentials, OAuth tokens) to any authenticated caller, or when a single role check gates access to the whole object rather than to each field. Without per-field authorization, an attacker may receive a payload that includes sensitive properties, effectively leaking secrets through a normal API response. This guide shows how to recognize and remediate such patterns by shaping responses to only include allowed fields based on the caller’s permissions, aligning with the OPLA (object-property level) defense in depth.
To fix, shape responses with explicit DTOs, implement field-level authorization, and enforce per-property checks via middleware or policy logic. Avoid returning sensitive fields unless the requester's role or claims authorize them. Use robust authentication to verify identity, store secrets in a secure backend rather than in memory or responses, and add tests that verify no sensitive properties leak for non-admin callers. Draw on lessons from CVE-2026-27131 to ensure that feature gates and per-field controls are correctly implemented in Go (Gin) services.
Affected Versions
Craft CMS Sprig Plugin: 2.0.0-2.15.1 and 3.0.0-3.15.1; mitigated in 2.15.2 and 3.15.2.
Code Fix Example
Go (Gin) API Security Remediation
package main
import (
"net/http"
"github.com/gin-gonic/gin"
)
type User struct {
ID int `json:"id"`
Name string `json:"name"`
Email string `json:"email"`
SSN string `json:"ssn"` // sensitive
Password string `json:"password"` // sensitive
OAuthToken string `json:"oauth_token"` // sensitive
}
type UserPublic struct {
ID int `json:"id"`
Name string `json:"name"`
Email string `json:"email"`
}
func getDemoUser() User {
return User{
ID: 1,
Name: "Alice",
Email: "[email protected]",
SSN: "123-45-6789",
Password: "supersecret",
OAuthToken: "token-abcdef",
}
}
// Vulnerable pattern: returns full user object including sensitive fields
func vulnerableGetUser(c *gin.Context) {
user := getDemoUser()
c.JSON(http.StatusOK, user)
}
// Fixed pattern: applies per-field authorization based on caller role (e.g., admin vs. regular user)
func fixedGetUser(c *gin.Context) {
user := getDemoUser()
role := c.GetHeader("X-Role") // e.g., admin, user
if role == "admin" {
// Admins can see all fields
c.JSON(http.StatusOK, user)
return
}
// Regular users only see non-sensitive fields
public := UserPublic{ID: user.ID, Name: user.Name, Email: user.Email}
c.JSON(http.StatusOK, public)
}
func main() {
r := gin.Default()
r.GET("/vulnerable/user/:id", vulnerableGetUser) // demonstrates vulnerable pattern
r.GET("/fixed/user/:id", fixedGetUser) // demonstrates fix (per-field)
_ = r
r.Run(":8080")
}