Nuxt: Unauthenticated CPU exhaustion parsing and hashing the Nuxt island endpoint body before hash validation

Nuxt is an open-source web development framework for Vue.js. From 3.1.0 until 3.21.10 and 4.5.1, the internal island renderer endpoint `/__nuxt_island/...` decodes and hashes attacker-controlled JSON body input with destr and ohash before validating the URL-resident hash. An unauthenticated `POST /__nuxt_island/_.json` with a large JSON body is fully read, parsed, hashed, and then rejected, which wastes CPU on Nitro single event loop and delays concurrent requests. No valid hash and no authentication are required. This issue is fixed in 3.21.10 and 4.5.1.