LibJS in Ladybird before f5a6704 mishandles the freeing of the vector that arguments_list references, leading to a use-after-free, and allowing remote attackers to execute arbitrary code via a crafted .js file. NOTE: the GitHub README says Ladybird is in a pre-alpha state, and only suitable for use by developers.
The product utilizes a shared resource in a concurrent manner but does not attempt to synchronize access to the resource.