The Paid Memberships Pro WordPress Plugin, version < 2.9.8, is affected by an unauthenticated SQL injection vulnerability in the 'code' parameter of the '/pmpro/v1/order' REST route.
The product constructs all or part of an SQL command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended SQL command when it is sent to a downstream component. Without sufficient removal or quoting of SQL syntax in user-controllable inputs, the generated SQL query can cause those inputs to be interpreted as SQL instead of ordinary user data.