# 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 Frequentemente explorada
- Impact: Crítico 1 regras de severidade crítica
- Prevention: Documentada 4 exemplos de correção

**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

Estratégias de prevenção para Cross-Site Scripting (XSS) baseadas em 1 regras de detecção do 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

- Executar código não autorizado
- Burlar mecanismo de proteção
- Ler dados da aplicação
- Modificar dados da aplicação

## Mitigations

- Use uma biblioteca ou framework testado que não permita esta fraqueza
- Entenda o contexto em que seus dados serão usados e a codificação esperada
- Use Content Security Policy (CSP) para mitigar o 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