fix(security): charge pop filter allocation to memoryLimit (CWE-770)

The `pop` array filter cloned the input via `[...toArray(v)]` without
charging `this.context.memoryLimit.use(...)`, bypassing the memoryLimit
DoS guard that its sibling filters (shift, unshift, compact, etc.) apply.
Mirror `shift` to account for the O(N) allocation.

Co-authored-by: Cursor <[email protected]>

src/filters/array.ts

@@ -88,8 +88,10 @@ export function unshift<T> (this: FilterImpl, v: T[], arg: T): T[] {
   return clone
 }
 
-export function pop<T> (v: T[]): T[] {
-  const clone = [...toArray(v)]
+export function pop<T> (this: FilterImpl, v: T[]): T[] {
+  const array = toArray(v)
+  this.context.memoryLimit.use(array.length)
+  const clone = [...array]
   clone.pop()
   return clone
 }

test/integration/liquid/dos.spec.ts

@@ -79,6 +79,11 @@ describe('DoS related', function () {
       await expect(liquid.parseAndRender(src, { array, count: 3 })).resolves.toBe('a a a a a a a a')
       await expect(liquid.parseAndRender(src, { array, count: 100 })).rejects.toThrow('memory alloc limit exceeded, line:1, col:26')
     })
+    it('should charge pop allocation to memoryLimit', async () => {
+      const array = Array(1e3).fill(0)
+      const liquid = new Liquid({ memoryLimit: 100 })
+      await expect(liquid.parseAndRender('{{ array | pop | size }}', { array })).rejects.toThrow('memory alloc limit exceeded')
+    })
     it('should charge strip_html input length to memoryLimit', () => {
       const liquid = new Liquid({ memoryLimit: 100 })
       expect(() => liquid.parseAndRenderSync('{{ s | strip_html }}', { s: 'a'.repeat(200) }))