Nbars

HotCRP is conference review software. Versions between October 2025 and January 2026 delivered documents of all types with inline Content-Disposition, causing them to be rendered in the user’s browser instead of being downloaded. This behavior was intended only for `text/plain`, `application/pdf`, `image/gif`, `image/jpeg`, and `image/png` files. However, adding `save=0` to the document URL could request inline delivery for any document. This made users vulnerable to cross-site scripting attacks when clicking a document link. Uploaded HTML or SVG documents could run in the viewer’s browser with access to their HotCRP credentials, allowing Javascript within those documents to make arbitrary calls to HotCRP’s API. Malicious documents could be uploaded to submission fields with “file upload” or “attachment” type, or as attachments to comments. PDF upload fields were not vulnerable. A search of documents uploaded to hotcrp.com found no evidence of exploitation. The issue was introduced in commit aa20ef288828b04550950cf67c831af8a525f508 and fixed in commit 8933e86c9f384b356dc4c6e9e2814dee1074b323.

A problem in the ECMAScript specification of async generators may lead to mis-implementation in a way that could present as a security issue, such as type confusion and pointer dereference. The internal async generator machinery calls regular promise resolver functions on IteratorResult objects, assuming that these objects will not be then-ables. However, these objects can be made then-able, triggering arbitrary behavior, including re-entering the async generator machinery in a way that violates some internal invariants.

A wrong assumption in Boa's implementation of `AsyncGenerator` can cause an uncaught exception on certain scripts. This occurs because the state of an `AsyncGenerator` object is assumed not to change while resolving a promise created by methods such as `%AsyncGeneratorPrototype%.next`, `%AsyncGeneratorPrototype%.return`, or `%AsyncGeneratorPrototype%.throw`. However, a carefully constructed code can trigger a state transition from a getter method for the promise's `then` property, causing the engine to fail an assertion of this assumption and resulting in an uncaught exception. This could be used to create a Denial Of Service attack in applications that run arbitrary ECMAScript code provided by an external user.

The issue is related to a type confusion in Async Generators, potentially leading to memory corruption and an exploitable crash. This could allow a remote attacker to cause a denial of service. The problem is associated with an error in the ECMA-262 specification.