io.github.sumup/mcp

What we checked

Six static checks, weighted by risk. Every result reflects only what could be observed in the published package and repository — never intent.

• Injection surface

  warn25% of grade

  Tool descriptions/manifest scanned for instruction-injection patterns (imperatives at the model, hidden text, 'ignore previous', data-exfil URLs).

  tool "create_checkout" param "currency" description: off-vendor URL in a description (en.wikipedia.org); capability text should not name where data goes. tool "create_checkout" param "date" description: off-vendor URL in a description (en.wikipedia.org); capability text should not name where data goes. tool "create_checkout" param "redirect_url" description: off-vendor URL in a description (developer.sumup.com); capability text should not name where data goes. tool "list_transactions_v2_1" param "changes_since" description: off-vendor URL in a description (en.wikipedia.org); capability text should not name where data goes. tool "list_transactions_v2_1" param "newest_time" description: off-vendor URL in a description (en.wikipedia.org); capability text should not name where data goes. tool "list_transactions_v2_1" param "oldest_time" description: off-vendor URL in a description (en.wikipedia.org); capability text should not name where data goes. tool "list_transactions" param "changes_since" description: off-vendor URL in a description (en.wikipedia.org); capability text should not name where data goes. tool "list_transactions" param "newest_time" description: off-vendor URL in a description (en.wikipedia.org); capability text should not name where data goes. tool "list_transactions" param "oldest_time" description: off-vendor URL in a description (en.wikipedia.org); capability text should not name where data goes. tool "list_payouts_v1" param "start_date" description: off-vendor URL in a description (en.wikipedia.org); capability text should not name where data goes. tool "list_payouts_v1" param "end_date" description: off-vendor URL in a description (en.wikipedia.org); capability text should not name where data goes. tool "list_payouts" param "start_date" description: off-vendor URL in a description (en.wikipedia.org); capability text should not name where data goes. tool "list_payouts" param "end_date" description: off-vendor URL in a description (en.wikipedia.org); capability text should not name where data goes.

• Supply chain

  warn25% of grade

  Package provenance: namespace verification, repo linkage, maintainer count, account age, postinstall scripts, typosquat distance.

  package name "@sumup/mcp" is edit-distance 2 from popular package "yup" (typosquat candidate)

• Credential hygiene

  fail15% of grade

  How the server takes secrets (env vs plaintext config vs hardcoded); secrets appearing in tool schemas.

  tool "create_sub_account" has a secret-shaped input parameter "password" — secrets must never be tool parameters (the model would supply/handle the credential). tool "update_sub_account" has a secret-shaped input parameter "password" — secrets must never be tool parameters (the model would supply/handle the credential). tool "create_merchant_member" has a secret-shaped input parameter "password" — secrets must never be tool parameters (the model would supply/handle the credential).

• Permission scope

  pass15% of grade

  Declared tools vs. breadth (filesystem, network, exec); flags shell-exec and unbounded filesystem access.

  No shell-exec, unbounded/sensitive filesystem, or download-and-run primitives found in scanned source. PASS = no static red flag. Static scanning is blind to code fetched or executed at runtime.

• Version behavior

  unscannable10% of grade

  Diff of tool definitions between versions; new permissions or changed descriptions in a patch release (the postmark-mcp class).

  no prior version to diff (first sight of io.github.sumup/[email protected]); version-drift / rug-pull cannot be evaluated. Cold-start risk is covered by point-in-time checks (injection_surface, supply_chain, credential_hygiene), not here.

• Transport config

  unscannable10% of grade

  Remote servers: TLS and auth mode (none/token/OAuth). Local servers: whether the manifest indicates it phones home.

  local stdio server: no remote transport or auth surface, and no phone-home/telemetry signal found in source. Absence of transport findings is NOT a safety guarantee — phone-home hosts can be constructed at runtime and defeat static analysis.