CVE-2025-0420 Overview
CVE-2025-0420 is a Cross-Site Scripting (XSS) vulnerability affecting Paraşüt Software's Paraşüt product. The flaw stems from improper neutralization of user-supplied input during web page generation, classified under [CWE-79]. An authenticated attacker with high privileges can inject malicious script content that executes in the browsers of other users. The vulnerability affects Paraşüt versions from 0.0.0.65efa44e through 20250204. The issue was published to the National Vulnerability Database (NVD) on September 17, 2025.
Critical Impact
Successful exploitation enables script execution in victim browser sessions, potentially exposing session data, credentials, or business information within the Paraşüt application context.
Affected Products
- Paraşüt Software Paraşüt (from 0.0.0.65efa44e through 20250204)
Discovery Timeline
- 2025-09-17 - CVE-2025-0420 published to NVD
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-0420
Vulnerability Analysis
The vulnerability resides in the Paraşüt web application, which fails to properly sanitize or encode user-supplied input before rendering it in HTML output. An attacker with authenticated, high-privilege access can inject JavaScript payloads through affected input fields. When another user renders the affected page, the browser executes the attacker-controlled script under the origin of the Paraşüt application.
Paraşüt is a Turkish cloud-based accounting and pre-accounting platform used by businesses to manage invoicing, expenses, and financial records. Script execution within this context can expose sensitive commercial and tax data.
The exploit vector is network-based and requires no user interaction beyond visiting the compromised page. The Exploit Prediction Scoring System (EPSS) currently indicates a low probability of exploitation in the near term.
Root Cause
The root cause is missing or inadequate output encoding when reflecting user-controlled input into HTML responses. Paraşüt does not neutralize special characters such as <, >, ", and ' before they are placed into the Document Object Model (DOM). This allows attacker-supplied markup and script tags to be parsed and executed by the victim's browser.
Attack Vector
An authenticated attacker with elevated privileges submits a payload containing JavaScript through a vulnerable input field within the Paraşüt interface. The payload is stored or reflected without adequate sanitization. When a legitimate user loads the affected view, the browser executes the injected script in the context of the Paraşüt domain. This can be used to hijack sessions, read displayed financial data, perform authenticated requests on behalf of the victim, or modify displayed content.
No public proof-of-concept exploit is currently available. Refer to the USOM Notification TR-25-0261 and Siber Güvenlik Notification TR-25-0261 for vendor coordination details.
Detection Methods for CVE-2025-0420
Indicators of Compromise
- HTTP request bodies or parameters containing script tags, javascript: URIs, or common XSS payload patterns such as onerror=, onload=, or <svg/onload>.
- Unexpected outbound requests from user browsers to attacker-controlled domains originating from the Paraşüt application context.
- Anomalous DOM modifications or script executions within pages served by the Paraşüt web interface.
Detection Strategies
- Inspect web server and reverse proxy access logs for request parameters containing HTML control characters or encoded script fragments.
- Deploy Web Application Firewall (WAF) rules that flag XSS signatures in POST bodies, query strings, and JSON fields sent to Paraşüt endpoints.
- Correlate high-privilege user activity with subsequent script-execution anomalies observed in end-user sessions.
Monitoring Recommendations
- Enable browser-side Content Security Policy (CSP) violation reporting and centralize the reports for review.
- Monitor privileged account activity for unusual content edits or bulk updates to fields rendered to other users.
- Ingest web application and identity logs into a centralized analytics platform to correlate XSS injection attempts with authentication events.
How to Mitigate CVE-2025-0420
Immediate Actions Required
- Upgrade Paraşüt to a version released after 20250204 that contains the vendor's XSS fix.
- Review privileged account access to Paraşüt and revoke unnecessary high-privilege permissions.
- Rotate session tokens and credentials for accounts that interacted with the application during the exposure window.
Patch Information
The vendor addressed the vulnerability in releases after build 20250204. Consult the USOM Notification TR-25-0261 and Siber Güvenlik Notification TR-25-0261 advisories for the fixed release identifier and vendor guidance. Apply the update as soon as maintenance windows allow.
Workarounds
- Enforce a strict Content Security Policy that disallows inline scripts and restricts script sources to trusted origins.
- Restrict high-privilege roles to a minimal set of trusted administrators until patching is complete.
- Deploy WAF rules that filter common XSS payloads on requests to Paraşüt input endpoints.
# Example restrictive Content-Security-Policy header
Content-Security-Policy: default-src 'self'; script-src 'self'; object-src 'none'; base-uri 'self'; frame-ancestors 'self'; report-uri /csp-report
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
