GHSA-9c3j-xm6v-j7j3

Given any pre-existing XSS / HTML injection vulnerability, an attacker can bypass the Content Security Policy's _script-src_ directive by uploading a crafted attachment to any issue that, when accessed via the _file_download.php_ link, will be downloaded with a valid JavaScript MIME type resulting in script execution.

The uploaded payload must be sniffed as a valid JavaScript MIME type by PHP finfo (see file_create_finfo() API function). Non-JavaScript MIME types will not get imported in a `<script>` tag by the browser, due to response header X-Content-Type-Options being set to _nosniff_, which requires all imported JavaScript files to be a valid JavaScript MIME type.

### Impact Cross-site scripting

### Patches - 9e3bee2e7b909f4e3596985892b8bc8bee9e0bfe

### Workarounds None

### Credits Thanks to siunam (Tang Cheuk Hei) for discovering and responsibly reporting the issue.