fix(shared): prevent prototype injection in set util

packages/shared/src/object.test.ts

@@ -144,6 +144,37 @@ describe('set', () => {
     expect(root.a).toBe(date)
     expect((root.a as Record<string, unknown>).b).toBe('value')
   })
+
+  it('does not pollute the prototype via __proto__', () => {
+    const root: Record<string, unknown> = {}
+    set(root, ['__proto__', 'polluted'], 'yes')
+
+    expect(({} as Record<string, unknown>).polluted).toBeUndefined()
+    expect(Object.getPrototypeOf(root)).toBe(Object.prototype)
+    expect(Object.hasOwn(root, '__proto__')).toBe(true)
+    // eslint-disable-next-line no-proto, no-restricted-properties
+    expect((root as any).__proto__).toEqual({ polluted: 'yes' })
+  })
+
+  it('does not pollute the prototype via constructor.prototype', () => {
+    const root: Record<string, unknown> = {}
+    set(root, ['constructor', 'prototype', 'polluted'], 'yes')
+
+    expect(({} as Record<string, unknown>).polluted).toBeUndefined()
+    expect((Object.prototype as any).polluted).toBeUndefined()
+    expect(Object.hasOwn(root, 'constructor')).toBe(true)
+    expect(root.constructor).toEqual({ prototype: { polluted: 'yes' } })
+  })
+
+  it('sets __proto__ as an own property instead of changing the prototype', () => {
+    const root: Record<string, unknown> = {}
+    set(root, ['__proto__'], 'value')
+
+    expect(Object.getPrototypeOf(root)).toBe(Object.prototype)
+    expect(Object.hasOwn(root, '__proto__')).toBe(true)
+    // eslint-disable-next-line no-proto, no-restricted-properties
+    expect((root as any).__proto__).toBe('value')
+  })
 })
 
 describe('omit', () => {

packages/shared/src/object.ts

@@ -81,16 +81,28 @@ export function set(
 
   for (let i = 0; i < path.length - 1; i++) {
     const key = path[i]!
-    const next = (current as Record<PropertyKey, unknown>)[key]
+    const next = Object.hasOwn(current, key) ? (current as Record<PropertyKey, unknown>)[key] : undefined
 
     if (!isTypescriptObject(next)) {
-      ;(current as Record<PropertyKey, unknown>)[key] = {}
+      const child = {}
+      defineOwnProperty(current, key, child)
+      current = child
+    }
+    else {
+      current = next
     }
-
-    current = (current as Record<PropertyKey, object>)[key]!
   }
 
-  ;(current as Record<PropertyKey, unknown>)[path.at(-1)!] = value
+  defineOwnProperty(current, path.at(-1)!, value)
+}
+
+function defineOwnProperty(object: object, key: PropertyKey, value: unknown): void {
+  Object.defineProperty(object, key, {
+    value,
+    writable: true,
+    enumerable: true,
+    configurable: true,
+  })
 }
 
 export function omit<T extends object, K extends keyof T>(