CVE-2025-8511: Portabilis i-Diario XSS Vulnerability

CVE-2025-8511 Overview

CVE-2025-8511 is a stored cross-site scripting (XSS) vulnerability [CWE-79] in Portabilis i-Diario 1.5.0. The flaw resides in the /diario-de-observacoes/ endpoint of the Observações component. Attackers can inject malicious script payloads through the Descrição parameter, which the application renders without proper sanitization. The exploit requires authenticated low-privilege access and user interaction to trigger. Public disclosure includes a proof-of-concept, and the vendor did not respond to coordinated disclosure attempts.

Critical Impact
Authenticated attackers can store malicious JavaScript that executes in the browsers of other users viewing the affected observation records, enabling session abuse and content manipulation within the i-Diario application.

Affected Products

Portabilis i-Diario 1.5.0
Component: Observações module
Endpoint: /diario-de-observacoes/

Discovery Timeline

2025-08-03 - CVE-2025-8511 published to the National Vulnerability Database
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-8511

Vulnerability Analysis

The vulnerability is a stored XSS flaw affecting the Observações feature of Portabilis i-Diario, a Brazilian school diary web application. User-supplied input to the Descrição (Description) field in the /diario-de-observacoes/ endpoint is persisted to the backend without adequate encoding. When another user later renders the stored observation, the browser executes any attacker-controlled JavaScript contained in the field. The attack can be launched remotely over the network by any authenticated user with permission to create observations.

Root Cause

The root cause is missing or insufficient output encoding of the Descrição parameter before it is reflected into the HTML response [CWE-79]. The application trusts stored user input and injects it into the Document Object Model (DOM) without context-aware escaping. There is no apparent Content Security Policy (CSP) that would mitigate inline script execution.

Attack Vector

An authenticated attacker submits a crafted payload containing JavaScript to the Descrição field of a new or edited observation record. The payload is stored server-side. When any user with access to the observation views the record, their browser parses the malicious markup and executes the script in the context of the i-Diario origin. This enables session token theft, forced actions on behalf of the victim, phishing overlays, or redirection. Technical reproduction steps are documented in the public GitHub Stored XSS Report.

No verified exploit code is included here. Refer to the CVE-2025-8511 GitHub documentation for proof-of-concept details.

Detection Methods for CVE-2025-8511

Indicators of Compromise

Stored observation records containing HTML tags such as <script>, <img onerror=>, or <svg onload=> in the Descrição field.
Unexpected outbound HTTP requests from user browsers to attacker-controlled domains while viewing /diario-de-observacoes/ pages.
Session anomalies affecting multiple users shortly after viewing specific observation records.

Detection Strategies

Review application and database logs for POST requests to /diario-de-observacoes/ with payloads containing script tags or JavaScript event handlers in the Descrição parameter.
Deploy a web application firewall (WAF) rule that flags common XSS signatures submitted to the i-Diario endpoints.
Perform periodic grep-style scans of stored observation records for HTML and JavaScript markup that should not appear in free-text fields.

Monitoring Recommendations

Enable verbose HTTP access logging on the i-Diario web tier and forward logs to a centralized analytics platform for retention and search.
Alert on anomalous spikes in outbound requests originating from authenticated user sessions.
Monitor browser-side Content Security Policy violation reports once CSP is deployed.

How to Mitigate CVE-2025-8511

Immediate Actions Required

Restrict access to the Observações creation and edit workflows to trusted users only until a patch is available.
Deploy a WAF rule to block requests containing HTML or JavaScript syntax in the Descrição parameter of /diario-de-observacoes/.
Audit existing observation records for stored script payloads and remove any malicious content.

Patch Information

No vendor patch is publicly available. Portabilis did not respond to the disclosure attempt documented in the VulDB entry #318610. Operators should contact the vendor directly and track future releases of i-Diario beyond version 1.5.0.

Workarounds

Implement a strict Content Security Policy that disallows inline scripts and restricts script sources to trusted origins.
Apply server-side input validation to reject HTML and JavaScript syntax in free-text fields.
Enforce context-aware output encoding at the template layer for all user-supplied strings rendered in HTML.

bash

# Example nginx WAF-style rule to block script tags in the Descrição parameter
location /diario-de-observacoes/ {
    if ($request_body ~* "(<script|onerror=|onload=|javascript:)") {
        return 403;
    }
    proxy_pass http://i-diario-backend;
}