GHSA-25h7-pfq9-p65f flatted vulnerable to unbounded recursion DoS in parse() revive phase

• npm flatted: < 3.4.0 → fixed in 3.4.0

Summary flatted's `parse()` function uses a recursive `revive()` phase to resolve circular references in deserialized JSON. When given a crafted payload with deeply nested or self-referential `$` indices, the recursion depth is unbounded, causing a stack overflow that crashes the Node.js process. Impact Denial of Service (DoS). Any application that passes untrusted input to `flatted.parse()` can be crashed by an unauthenticated attacker with a single request. flatted has ~87M weekly npm downloads and is used as the circular-JSON serialization layer in many caching and logging libraries. Proof of Concept ```javascript const flatted = require('flatted'); // Build deeply nested circular reference chain const depth = 20000; const arr = new Array(depth + 1); arr[0] = '{"a":"1"}'; for (let i = 1; i <= depth; i++) { arr[i] = `{"a":"${i + 1}"}`; } arr[depth] = '{"a":"leaf"}'; const payload = JSON.stringify(arr); flatted.parse(payload); // RangeError: Maximum call stack size exceeded ``` Fix The maintainer has already merged an iterative (non-recursive) implementation in PR #88, converting the recursive `revive()` to a stack-based loop. Affected Versions All versions prior to the PR #88 fix.