Blind NoSQL injection via date variable in Chartbrew embedded chart

Chartbrew is an open-source web application that can connect directly to databases and APIs and use the data to create charts. Prior to 5.2.3, a date-typed MongoDB variable placed inside a quoted query placeholder was inserted as an unescaped string, unlike the safely escaped or coerced string, number, and Boolean branches. The vulnerable surface is mongoDB-backed public, shareable, or embedded charts processed by date-variable substitution. An unauthenticated user supplies a crafted URL filter to a public, shareable, or embedded MongoDB chart whose query places a date-typed variable in a quoted literal. The crafted date value breaks out of the quoted literal and changes query logic; the chart's returned row count becomes a Boolean oracle for character-by-character field extraction. The chart must be externally reachable and use the vulnerable date-in-quoted-placeholder branch. Extraction is read-only and limited to one queried collection per request, and it requires neither an account nor a known field value. The blind oracle can disclose any field in the queried collection, including secrets the chart does not display. This issue is fixed in version 5.2.3.