Forty pounds of sofa insurance

The mistake

The checkout adds an opt-in insurance add-on as a checkbox that ships pre-checked instead of empty, so the affirmative-consent step is inverted: silence is read as agreement rather than the customer having to actively tick it. Because this default-checked state was applied globally to every checkbox component in the shop rather than scoped to genuine confirmations like a newsletter signup, the same styling and logic silently attached a paid add-on to every order, and nobody flagged it because visually it looked identical to the low-stakes checkboxes it was tested against.