NFT Metadata Validation Remediation
Overview
Related Detector: NFT Metadata Validation
Unvalidated metadata operations enable counterfeit NFTs. The fix is to validate update authority, verify creator signatures, and check collection membership before any metadata modification.
Impact. Modifying an NFT’s metadata without checking update authority, creator signatures, and collection membership lets an attacker rewrite its name, image, or collection — counterfeiting a valuable asset or grafting a fake into a trusted collection. Because marketplaces and buyers treat on-chain metadata as the source of provenance, forged metadata translates directly into fraudulent sales.
Recommended Fix
#[derive(Accounts)]
pub struct UpdateMetadata<'info> {
#[account(mut, has_one = update_authority)]
pub metadata: Account<'info, NftMetadata>,
pub update_authority: Signer<'info>,
}
pub fn update(ctx: Context<UpdateMetadata>, new_uri: String) -> Result<()> {
require!(new_uri.len() <= MAX_URI_LEN, UriTooLong);
ctx.accounts.metadata.uri = new_uri;
Ok(())
}Alternative Mitigations
Use the NFT metadata program CPI
Delegate metadata operations to the standard NFT metadata program which enforces all validations:
invoke(
&mpl_token_metadata::instruction::update_metadata_accounts_v2(...),
accounts,
)?;Common Mistakes
Mistake: Not Validating URI Format
// WRONG: accepts any string as URI, including empty or malicious
metadata.uri = user_provided_uri;Validate URI length and optionally format before storage.