CWE-183 Permissive List of Allowed Inputs

What this means

SiteShadow flagged an allowlist/validation rule that is too permissive. An allowlist is only effective if it's narrow enough to exclude dangerous values.

Why it matters

Overly broad allowlists can admit unsafe input.

• Injection bypass when the "allowed" set still contains dangerous characters/structures.
• Policy bypass when allowlists accept unexpected schemes/hosts/types (e.g., allowing file: or javascript:).

Safer examples

1) Make allowlists explicit and small

Prefer "only these values" over "anything except these values."

2) Apply context-specific allowlists

URLs: allowlist schemes/hosts. Filenames: allowlist characters and extensions. Enums: allowlist values.

3) Add tests for bypasses

Include "naughty strings" and known bypass payloads to ensure the allowlist stays strict over time.

How SiteShadow detects it (high level)

• Detects allowlist patterns that include overly broad wildcards or dangerous values.
• Flags when allowlists are used for security decisions but do not meaningfully constrain input.

References

• CWE-183: https://cwe.mitre.org/data/definitions/183.html

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