Know every vulnerabilitybefore it knows you.
DevGuard continuously monitors your dependencies and alerts you when CVEs like this one affect your stack — with real-time threat intelligence built for developers.
GHSA-jwf8-pv5p-vhmc
No affected components available
Summary
Excel file attachments are previewed in an unsafe way. A crafted XLSX file payload can be used to cause the sheetjs function sheet_to_html to embed an XSS payload into the generated HTML. This is subsequently added to the DOM unsanitized via @html causing the payload to trigger.
Details
The function used to convert XLSX documents to HTML for preview does not perform any input validation or sanitisation for the generated HTML
https://github.com/open-webui/open-webui/blob/a7271532f8a38da46785afcaa7e65f9a45e7d753/src/lib/components/common/FileItemModal.svelte#L120-L133
XLSX attachments are processed by this function, converted to HTML with XLSX.utils.sheet_to_html before ultimately being assigned to the variable excelHtml. Later there is logic that causes this to be assigned directly to the DOM when the preview tab is selected.
https://github.com/open-webui/open-webui/blob/a7271532f8a38da46785afcaa7e65f9a45e7d753/src/lib/components/common/FileItemModal.svelte#L358-L400
PoC
A python script to generate a payload file is as follows:
import xlsxwriter
payload = '<img src=x onerror="alert(\'XSS Triggered by XLSX file\')">'
workbook = xlsxwriter.Workbook('xss_payload.xlsx')
worksheet = workbook.add_worksheet()
payload_format = workbook.add_format()
worksheet.write_rich_string('A1',
'This cell contains a hidden payload: ',
payload_format, payload
)
worksheet.write('A2', 'This is a safe cell.')
worksheet.write('B1', 'Column B')
workbook.close()
Upload the generated file as an attachment to a chat, open the file modal, and click preview. Observe the XSS triggers. <img width="2444" height="1386" alt="image" src="https://github.com/user-attachments/assets/8400efb0-ea6f-4878-abdb-4c2fe529241f" /> This same process can be triggered in shared chats, allowing the payload to be distributed to victims. <img width="2386" height="1646" alt="image" src="https://github.com/user-attachments/assets/d0eda49c-8fcf-4fc4-bbb0-c8951b0369c3" />
Impact
Any user can create a weaponised chat that can be shared and subsequently used to target other users.
Low privilege users are at risk of having their session taken over by a payload that reads their token from local storage and exfiltrates it to an attacker controlled server.
Admins are at risk of exposing the server to RCE via same chain described in GHSA-w7xj-8fx7-wfch.
Caveats
The file attachment in the shared chat must be opened and previewed to trigger the vulnerability.
Recommendation
Sanitise the generated HTML with DOMPurify before assigning it to the DOM.
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker needs basic access or low-level privileges. The attacker needs the user to perform some action, like clicking a link. The impact is confined to the system where the vulnerability exists. There is a high impact on the confidentiality of the information. There is a high impact on the integrity of the data.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
Browse More
Continuously monitor your dependencies and get alerted when vulnerabilities like this one affect your stack.
Checkout DevGuard