Kysely is a type-safe TypeScript SQL query builder. In versions 0.28.12 and 0.28.13, the `sanitizeStringLiteral` method in Kysely's query compiler escapes single quotes (`'` → `''`) but does not escape backslashes. On MySQL with the default `BACKSLASH_ESCAPES` SQL mode, an attacker can inject a backslash before a single quote to neutralize the escaping, breaking out of the JSON path string literal and injecting arbitrary SQL. Version 0.28.14 fixes the issue.

Affected: npm: kysely

## Summary

The `sanitizeStringLiteral` method in Kysely's query compiler escapes single quotes (`'` → `''`) but does not escape backslashes. On MySQL with the default `BACKSLASH_ESCAPES` SQL mode, an attacker can inject a backslash before a single quote to neutralize the escaping, breaking out of the JSON path string literal and injecting arbitrary SQL.

## Details

When a user calls `.key(value)` on a JSON path builder, the value flows through:

1. `JSONPathBuilder.key(key)` at `src/query-builder/json-path-builder.ts:166` stores the key as a `JSONPathLegNode` with type `'Member'`.

2. During compilation, `DefaultQueryCompiler.visitJSONPath()` at `src/query-compiler/default-query-compiler.ts:1609` wraps the full path in single quotes (`'$...'`).

3. `DefaultQueryCompiler.visitJSONPathLeg()` at `src/query-compiler/default-query-compiler.ts:1623` calls `sanitizeStringLiteral(node.value)` for string values (line 1630).

4. `sanitizeStringLiteral()` at `src/query-compiler/default-query-compiler.ts:1819-1821` only doubles single quotes:

```typescript // src/query-compiler/default-query-compiler.ts:121 const LIT_WRAP_REGEX = /'/g

// src/query-compiler/default-query-compiler.ts:1819-1821 protected sanitizeStringLiteral(value: string): string { return value.replace(LIT_WRAP_REGEX, "''") } ```

The `MysqlQueryCompiler` does not override `sanitizeStringLiteral` — it only overrides `sanitizeIdentifier` for backtick escaping.

**The bypass mechanism:**

In MySQL's default `BACKSLAS…