fix(isCreditCard): anchor Mastercard alternation so partial strings are rejected - #2854
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What & Why
isCreditCard("5108")(and any trailing-junk / short string beginning with 51-55, e.g."5108foo") incorrectly returnedtruebecause the Mastercard regex's|alternation was not grouped, so only the first branch carried the^anchor. This let any string starting with a valid 2-series BIN prefix pass regardless of length. It is a correctness/security bug for any call site that trustsisCreditCardfor format validation.Changes
src/lib/isCreditCard.js: wrap the Mastercard alternation in(?:...)so^and$anchor the whole pattern. Valid 16-digit Mastercard numbers (incl. 2-series 2221–2720) are unaffected.Test plan
mocha --grep "credit card"passes (9 passing).isCreditCard("5108")→false;isCreditCard("5108foo")→false.isCreditCard("5398228707871527")andisCreditCard("2222155765072228")→true(unchanged).