Securaity Browse advisories
SA-26-292 High

Open WebUI: Open WebUI vulnerable to Stored XSS via iFrame in citations model

Open WebUI

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Severity
High, CVSS 7.3
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:N
Record
CVE-2026-26192
Affects
Open WebUI
Known exploited
Not listed in the CISA Known Exploited Vulnerabilities catalog
Published
Record first published by the source
July 7, 2026
Source last modified
July 7, 2026

Description

Summary

Manually modifying chat history allows setting the html property within document metadata. This causes the frontend to enter a code path that treats document contents as HTML, and render them in an iFrame when the citation is previewed. This allows stored XSS via a weaponised document payload in a chat. The payload also executes when the citation is viewed on a shared chat.

Details

The vulnerability stems from how iFrame are implemented here: https://github.com/open-webui/open-webui/blob/6f1486ffd0cb288d0e21f41845361924e0d742b3/src/lib/components/chat/Messages/Citations/CitationModal.svelte#L163-L170 The html attribute can be controlled by a user who manually edits the chat history. Since allow-scripts and allow-same-origin are harcoded here the sandboxing offers essentially no protection.

PoC

Create an arbitrary chat with a file upload attached: <img width="2462" height="1148" alt="image" src="https://github.com/user-attachments/assets/fad83c74-036d-41b8-bc44-87bf2a538b21" /> Edit the response <img width="768" height="206" alt="image" src="https://github.com/user-attachments/assets/41a7342a-cc41-433e-8820-0bc6ed08ddd7" /> <img width="2142" height="796" alt="image" src="https://github.com/user-attachments/assets/fb731111-e082-4172-80d1-34cff6b2a511" /> Before saving, configure the browser to use an HTTP proxy tool (Burp/Caido/ZAP) and intercept the save request. Find the object within the history and then messages objects (not the messages array) that contains the document source. <img width="2122" height="1388" alt="image" src="https://github.com/user-attachments/assets/1b4fbced-a6de-414d-b063-9cae44e3f449" /> Add html: true to metadata, update the document to an XSS payload, and forward the request. <img width="2240" height="1358" alt="image" src="https://github.com/user-attachments/assets/fd27971b-f707-458f-a14d-254f9f3ad1fa" /> Observe the payload is rendered in the iFrame and the javascript executes. <img width="2698" height="1696" alt="image" src="https://github.com/user-attachments/assets/b4e31cb4-d4cc-41a9-be42-802e9b1a798d" /> The payload also executes when viewed from a shared version of the chat. <img width="2742" height="1258" alt="image" src="https://github.com/user-attachments/assets/92ee501d-8f14-4c32-8f3c-f4d3ca304ee5" />

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 https://github.com/advisories/GHSA-w7xj-8fx7-wfch.

Caveats

The victim must expand the sources and click the document containing the payload to trigger this issue.

Description quoted from the NVD record.

Who is affected

Open WebUI is a chat program used in a web browser. This flaw is in the part that shows a preview of a document cited in a chat. No affected versions are named for this flaw. Any user with an account can tamper with a saved chat so that a cited document carries harmful code. The code runs when another person opens the chat's sources and clicks that document, including in a shared chat. This could let an attacker take over a regular user's login session and, when the victim is an admin, run commands on the server. This flaw is rated High.

What to do

  1. The person who installed or runs Open WebUI for your organization should handle this, or the IT provider who manages it for you.
  2. No fixed version is named for this flaw yet, so check the vendor advisory linked on this page for a fixed release.
  3. When a fixed release is available, install it on every copy of Open WebUI your organization runs.
  4. If an IT provider or vendor runs Open WebUI for your organization, send them this advisory and ask when the update will be done.

Analysis written from the source record as of July 7, 2026 and reviewed before publishing.

Sources

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