Python Code Checker: Free Online Security and Syntax Analysis

CodeSlick is a free Python code checker built for security, not just syntax. While tools like Pylint and Flake8 focus on style and type errors, CodeSlick performs 47 security checks that detect real vulnerabilities in Python applications—the kind that lead to data breaches and server compromises.

When you scan Python code with CodeSlick, it analyzes:

• Injection vulnerabilities: SQL injection via raw queries, command injection through os.system() and subprocess, and code injection via eval(), exec(), and pickle.loads().
• Framework-specific checks: Django ORM bypass patterns, Flask debug mode in production, Jinja2 template injection, and CSRF protection misconfigurations.
• Insecure deserialization: pickle, yaml.load() without SafeLoader, and marshal usage with untrusted data.
• Path traversal: File operations with user-controlled paths, open() calls without sanitization, and unsafe os.path.join() patterns.
• Hardcoded secrets: Django SECRET_KEY, database passwords, API tokens, and AWS credentials embedded in source files.
• Cryptographic weaknesses: Use of MD5, SHA-1, DES, and insecure random number generators (random instead of secrets).

Every finding maps to CWE identifiers, CVSS 3.1 severity scores, and the OWASP Top 10:2025 categories. CodeSlick also detects AI-generated Python code, catching hallucinations and insecure patterns from LLM tools.

CodeSlick's Python analyzer understands framework-specific patterns. It does not just grep for dangerous function names—it analyzes data flow to reduce false positives and catch real vulnerabilities.

What CodeSlick Detects

# CodeSlick flags: SQL Injection (CWE-89, CVSS 9.8)
cursor.execute("SELECT * FROM users WHERE id = " + user_id)

# CodeSlick flags: Command Injection (CWE-78, CVSS 9.8)
os.system("ping " + request.args.get("host"))

# CodeSlick flags: Insecure Deserialization (CWE-502, CVSS 9.8)
data = pickle.loads(request.data)

# CodeSlick flags: SSTI (CWE-1336, CVSS 9.8)
return render_template_string(user_input)

Django and Flask Coverage

CodeSlick checks for framework-specific vulnerabilities that generic Python linters miss:

• Django: Raw SQL via .raw() and .extra(), DEBUG = True in production, missing @login_required, mark_safe() with user input, and CSRF exemption misuse.
• Flask: Debug mode enabled, secret_key hardcoded, Jinja2 render_template_string() with user input, and missing CSRF protection on forms.
• FastAPI: Missing input validation on path parameters, unprotected endpoints, and insecure CORS configurations.

The 47 checks also cover dependency scanning for pip packages, detecting known vulnerable versions and malicious packages through OSV.dev integration.

Python's simplicity and readability make it the most popular language for web development, data science, and automation—but that same popularity makes it a prime target:

• PyPI supply chain attacks (2022-2024): Hundreds of malicious packages uploaded to PyPI using typosquatting (e.g., reqeusts instead of requests). CodeSlick's malicious package scanner covers 66 known malicious packages plus OSV.dev real-time data.
• Django SQL injection (CVE-2022-28346): A vulnerability in QuerySet.annotate(), aggregate(), and extra() allowed SQL injection through crafted column aliases. CodeSlick flags all raw SQL and ORM bypass patterns.
• Pickle deserialization RCE: Python's pickle module executes arbitrary code during deserialization. Multiple production systems have been compromised through pickled data in Redis caches, message queues, and ML model files.

These vulnerabilities are Python-specific. A generic code checker would miss the Django ORM nuances or the pickle deserialization risk. CodeSlick's 47 checks are purpose-built for the Python threat landscape.

CodeSlick's Python code checker is free with no account required. Paste your Python code at /analyze, select Python, and get a full security report in under 3 seconds.

Every scan includes:

• 47 security checks with CWE classification, CVSS severity, and OWASP Top 10:2025 mapping
• Django, Flask, and FastAPI coverage that catches framework-specific misconfigurations
• AI code detection using 150 signals to identify LLM-generated code and hallucination patterns
• AI-powered fix suggestions that generate secure replacement code tailored to your framework
• Dependency scanning for pip packages with malicious package detection

For automated security, CodeSlick offers a GitHub App for pull request scanning and a CLI for pre-commit hooks. Start with the free web scanner to see what 47 Python security checks find in your code.