phpMyFAQ has SQL Injection in `StopWords::add()` — Unescaped Stop Word Insertion

phpMyFAQ is an open source FAQ web application. The `StopWords::add()` method inversions prior to 4.1.6 builds a SQL `INSERT` statement using `sprintf()` and inserts the user-supplied stop word value directly into the query string without calling the application's database escaping function on it. A sibling method, `StopWords::update()`, which modifies an existing stop word, correctly escapes the same kind of input. The omission is isolated to the `add()` (insert) code path. An authenticated administrator who can reach the stop-word management feature can submit a crafted value as the "word" parameter that breaks out of the SQL string literal and injects arbitrary SQL, including statements to drop tables, exfiltrate data, or modify other rows in the database. Version 4.1.6 fixes the issue.