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

### Impact

SQL injection can occur when all of the following conditions are met:

1. The non-default simple protocol is used. 2. A placeholder for a numeric value must be immediately preceded by a minus. 3. There must be a second placeholder for a string value after the first placeholder; both must be on the same line. 4. Both parameter values must be user-controlled.

e.g.

Simple mode must be enabled:

```go // connection string includes "prefer_simple_protocol=true" // or // directly enabled in code config.ConnConfig.PreferSimpleProtocol = true ```

Parameterized query:

```sql SELECT * FROM example WHERE result=-$1 OR name=$2; ```

Parameter values:

`$1` => `-42` `$2` => `"foo\n 1 AND 1=0 UNION SELECT * FROM secrets; --"`

Resulting query after preparation:

```sql SELECT * FROM example WHERE result=--42 OR name= 'foo 1 AND 1=0 UNION SELECT * FROM secrets; --'; ```

### Patches

The problem is resolved in v4.18.2.

### Workarounds

Do not use the simple protocol or do not place a minus directly before a placeholder.