MIT Lifelong Kindergarten Scratch scratch-vm before 0.2.0-prerelease.20200714185213 loads extension URLs from untrusted project.json files with certain _ characters, resulting in remote code execution because the URL's content is treated as a script and is executed as a worker. The responsible code is getExtensionIdForOpcode in serialization/sb3.js. The use of _ is incompatible with a protection mechanism in older versions, in which URLs were split and consequently deserialization attacks were prevented.
NOTE: the scratch.mit.edu hosted service is not affected because of the lack of worker scripts.
{
"github_reviewed_at": "2020-07-27T19:53:24Z",
"severity": "CRITICAL",
"cwe_ids": [
"CWE-502"
],
"github_reviewed": true,
"nvd_published_at": null
}