CVE-2025-5513: Shiyi-blog XSS Vulnerability

CVE-2025-5513 Overview

CVE-2025-5513 is a stored cross-site scripting (XSS) vulnerability affecting quequnlong shiyi-blog through version 1.2.1. The flaw resides in the comment submission endpoint at /dev-api/api/comment/add, where the content parameter is not properly sanitized before being stored and rendered. An authenticated remote attacker can inject arbitrary JavaScript that executes in the browser of any user who views the affected comment thread. The issue is classified under [CWE-79] (Improper Neutralization of Input During Web Page Generation). The vendor was contacted prior to public disclosure but did not respond, and the exploit details have been made public.

Critical Impact
Attackers can persistently inject JavaScript into blog comments, enabling session hijacking, credential theft, and drive-by client-side attacks against every visitor who loads the compromised page.

Affected Products

quequnlong shiyi-blog versions up to and including 1.2.1
Deployments exposing the /dev-api/api/comment/add endpoint
Any downstream fork retaining the unsanitized comment handler

Discovery Timeline

2025-06-03 - CVE-2025-5513 published to the National Vulnerability Database (NVD)
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-5513

Vulnerability Analysis

The vulnerability is a stored (persistent) XSS in the shiyi-blog comment subsystem. The application accepts user-supplied comment content through a POST request to /dev-api/api/comment/add and stores the value without HTML encoding or script neutralization. When the comment is later rendered in the blog view, the injected markup is returned inside the page body and executed by the browser as part of the trusted origin.

Because the payload persists in the backend datastore, exploitation does not require any social engineering beyond a normal page visit. Any account that can post a comment can plant a payload that fires for administrators and regular readers alike. Successful exploitation can lead to session token theft, forced actions performed as the victim, defacement, or redirection to attacker-controlled infrastructure.

Root Cause

The root cause is missing output encoding and input sanitization on the content field handled by the comment controller. The application trusts client-supplied HTML instead of applying context-aware escaping or an allowlist-based sanitizer before persistence and rendering. This maps directly to [CWE-79].

Attack Vector

Exploitation is network-based and requires low privileges (a user account capable of posting comments) plus user interaction from the victim who views the page. The attacker submits a crafted comment containing JavaScript in the content parameter through the public API endpoint. Additional technical details are documented in the GitHub Stored XSS Section and the VulDB #310927 Details entry.

Detection Methods for CVE-2025-5513

Indicators of Compromise

Comment records containing <script>, onerror=, onload=, javascript:, or encoded variants such as <script in the content column
POST requests to /dev-api/api/comment/add with payload bodies exceeding normal comment length or containing HTML tags
Outbound requests from user browsers to unfamiliar domains immediately after loading a blog article page
Anomalous session token exfiltration patterns originating from the blog origin

Detection Strategies

Perform pattern matching on stored comment content for HTML tags and JavaScript event handlers
Inspect web server access logs for POST requests to the comment endpoint originating from low-reputation IP addresses
Deploy a web application firewall (WAF) rule set that flags XSS signatures targeting the comment API path
Correlate comment submissions with subsequent atypical client-side behavior such as unexpected cookie access

Monitoring Recommendations

Enable Content Security Policy (CSP) reporting to capture blocked inline script execution attempts
Alert on repeated 200 responses to /dev-api/api/comment/add from a single source within short intervals
Monitor administrative account activity for unexpected actions initiated shortly after viewing comments

How to Mitigate CVE-2025-5513

Immediate Actions Required

Restrict or disable the /dev-api/api/comment/add endpoint until a vendor fix is available
Purge existing comment records for stored HTML payloads and JavaScript handlers
Require authenticated moderation review before comments are rendered to other users
Enforce a strict Content Security Policy that blocks inline scripts on all blog pages

Patch Information

No vendor patch is currently available. The maintainer of quequnlong shiyi-blog did not respond to the coordinated disclosure attempt referenced in the VulDB #310927 Incident record. Operators should track the GitHub Blog Post for future updates and consider forking the project to apply local patches.

Workarounds

Add server-side sanitization using a vetted HTML sanitizer library before persisting comment content
Apply context-aware output encoding when rendering comment bodies in the frontend template
Deploy a WAF rule that rejects requests to /dev-api/api/comment/add containing <, >, or javascript: sequences
Set HttpOnly and SameSite=Strict attributes on session cookies to reduce theft impact

bash

# Example WAF rule (ModSecurity) blocking XSS payloads to the comment endpoint
SecRule REQUEST_URI "@streq /dev-api/api/comment/add" \
  "id:1005513,phase:2,deny,status:403,\
   msg:'CVE-2025-5513 shiyi-blog comment XSS attempt',\
   chain"
  SecRule ARGS:content "@rx (?i)(<script|onerror=|onload=|javascript:)" \
    "t:none,t:urlDecodeUni,t:htmlEntityDecode"