Affected: Go: github.com/jackc/pgx/v5, Go: github.com/jackc/pgx/v4, Go: github.com/jackc/pgx

### Impact

SQL Injection can occur when:

1. The non-default simple protocol is used. 2. A dollar quoted string literal is used in the SQL query. 3. That string literal contains text that would be would be interpreted as a placeholder outside of a string literal. 4. The value of that placeholder is controllable by the attacker.

e.g.

```go attackValue := `$tag$; drop table canary; --` _, err = tx.Exec(ctx, `select $tag$ $1 $tag$, $1`, pgx.QueryExecModeSimpleProtocol, attackValue) ```

This is unlikely to occur outside of a contrived scenario.

### Patches

The problem is resolved in v5.9.2.

### Workarounds

Do not use the simple protocol to execute queries matching all the above conditions.