What kind of vulnerability is it? Who is impacted? In Hardened JavaScript, programs can "harden" objects to safely share objects with co-tenant programs without risk of these other programs tampering with their API surface. Hardening does not guarantee that objects are pure or immutable, so a hardened "Map", for example is superficially tamper-proof, but any party holding a reference to the object can both read and write its contents. Based on this precedent, and because "TypedArray" instances cannot be frozen with "Object.isFrozen", "harden" does not "freeze" "TypedArrays" and instead makes them non-extensible and makes all non-indexed properties non-writable and non-configurable. This is consistent with the treatment of "Map" because the indexed properties represent mutable content and non-indexed properties represent the API. Due to a defect in "harden", properties that have names that parse as numbers but are not the same as the canonical representation of those numbers, as in ""+0"" and """" which are both equivalent to their canonical number ""0"", remain writable after hardening. Any program treating one of these properties as part of its API and relying on "harden" to prevent modifications would be vulnerable to an API pollution attack, affecting only instances shared by mutually suspicious parties. Unlike a "Map", a hardened "TypedArray" can only have numbers for content. Any program that is sharing hardened "TypedArrays" between co-tentant programs and relying on harden to only allow these programs to communicate exclusively by changing numbers within the bounds of the TypedArray, may inadvertently have arranged for a mechanism for a pair of third-parties to communicate arbitrary objects on these other properties.