Affected versions of yui are vulnerable to cross-site scripting in the uploader.swf and io.swf utilities, via script injection in the url.
YUI has published their recommendation to fix this issue. Their recommendation is to:
{
"cwe_ids": [
"CWE-79"
],
"github_reviewed": true,
"github_reviewed_at": "2020-08-31T18:19:38Z",
"nvd_published_at": null,
"severity": "MODERATE"
}