# Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') (CWE-79)

The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.

**Stack:** Python

- Prevalence: Alta Frecuentemente explotada
- Impact: Crítico 1 reglas de severidad crítica
- Prevention: Documentada 4 ejemplos de corrección

**OWASP:** Injection (A03:2021-Injection) - #3

## Description

Cross-site scripting (XSS) vulnerabilities occur when untrusted data enters a web application and is sent to a web browser without proper validation or encoding. XSS allows attackers to execute scripts in the victim's browser which can hijack user sessions, deface web sites, or redirect the user to malicious sites.

## Prevention

Estrategias de prevención para Cross-Site Scripting (XSS) basadas en 1 reglas de detección de Shoulder.

### Python

Use template rendering with auto-escaping or html.escape() for manual escaping

## Warning Signs

- [HIGH] untrusted user input being rendered in HTML responses without proper
escaping

## Consequences

- Ejecutar código no autorizado
- Eludir mecanismo de protección
- Leer datos de la aplicación
- Modificar datos de la aplicación

## Mitigations

- Usa una biblioteca o framework verificado que no permita esta debilidad
- Comprende el contexto en el que se usarán tus datos y la codificación que se espera
- Usa Content Security Policy (CSP) para mitigar el impacto

## Detection

- Total rules: 4
- Critical: 1
- Languages: javascript, typescript, python

## Rules by Language

### Python (1 rules)

- **Cross-Site Scripting (XSS) in Templates** [HIGH]: Detects untrusted user input being rendered in HTML responses without proper
escaping.
  - Remediation: Use template rendering with auto-escaping, or escape manually with html.escape().

```python
import html
safe_text = html.escape(user_input)
```

Learn more: https://shoulder.dev/learn/python/cwe-79/xss