langgenius/dify
1
0
Fork 0
mirror of https://github.com/langgenius/dify.git synced 2026-07-21 12:05:30 -04:00
Code Issues 775 Packages Projects Releases 10 Wiki Activity

add security headers for file-preview to prevent cross-site scripting (XSS) injection #20673

New Issue
Closed
opened 2026-02-21 20:08:24 -05:00 by yindo · 1 comment
yindo commented 2026-02-21 20:08:24 -05:00
Owner
Copy Link
Copy Source

Originally created by @ruanimal on GitHub (Nov 28, 2025).

Self Checks

  • I have read the Contributing Guide and Language Policy.
  • I have searched for existing issues search for existing issues, including closed ones.
  • I confirm that I am using English to submit this report, otherwise it will be closed.
  • Please do not modify this template :) and fill in all the required fields.

1. Is this request related to a challenge you're experiencing? Tell me about your story.

The current file preview interface is at risk of XSS injection. If a user uploads malicious HTML, SVG, or XML files, it may trigger various attacks.

There is a risk of XSS injection in the current file preview interface. If a user uploads malicious HTML, SVG, or XML files, it may trigger various attacks.

Reproduction method:

  • Upload a malicious file as a workflow parameter and open the file preview link.

Example file:

alert.svg

xss_test.html

2. Additional context or comments

No response

3. Can you help us with this feature?

  • I am interested in contributing to this feature.
Originally created by @ruanimal on GitHub (Nov 28, 2025). ### Self Checks - [x] I have read the [Contributing Guide](https://github.com/langgenius/dify/blob/main/CONTRIBUTING.md) and [Language Policy](https://github.com/langgenius/dify/issues/1542). - [x] I have searched for existing issues [search for existing issues](https://github.com/langgenius/dify/issues), including closed ones. - [x] I confirm that I am using English to submit this report, otherwise it will be closed. - [x] Please do not modify this template :) and fill in all the required fields. ### 1. Is this request related to a challenge you're experiencing? Tell me about your story. The current file preview interface is at risk of XSS injection. If a user uploads malicious HTML, SVG, or XML files, it may trigger various attacks. There is a risk of XSS injection in the current file preview interface. If a user uploads malicious HTML, SVG, or XML files, it may trigger various attacks. Reproduction method: - Upload a malicious file as a workflow parameter and open the file preview link. Example file: [alert.svg](https://github.com/user-attachments/assets/178ea947-d247-450e-89cc-c3f4d3af678c) [xss_test.html](https://github.com/user-attachments/files/23822692/xss_test.html) ### 2. Additional context or comments _No response_ ### 3. Can you help us with this feature? - [x] I am interested in contributing to this feature.
yindo added the 💪 enhancement label 2026-02-21 20:08:24 -05:00
yindo closed this issue 2026-02-21 20:08:24 -05:00
yindo commented 2026-02-21 20:08:25 -05:00
Author
Owner
Copy Link
Copy Source

@dosubot[bot] commented on GitHub (Nov 28, 2025):

To mitigate XSS in file previews, you should add security headers to the Flask Response objects in the preview endpoints. The most effective headers are:

  • Content-Security-Policy (CSP): Restricts what scripts and resources can run. For file previews, a safe default is Content-Security-Policy: default-src 'none'; sandbox.
  • X-Content-Type-Options: nosniff: Prevents browsers from interpreting files as a different MIME type, which is critical for SVG/HTML/XML.
  • X-Frame-Options: DENY: Prevents the file from being embedded in an iframe, blocking clickjacking and some XSS vectors.
  • Referrer-Policy: no-referrer: Reduces information leakage.

In the Dify codebase, file previews are served in Flask controllers like api/controllers/files/image_preview.py and api/controllers/service_api/app/file_preview.py. Currently, these endpoints set headers like Content-Type and Content-Disposition but do not set any security headers (source).

You can add these headers directly when constructing the Response object, for example:

response.headers['Content-Security-Policy'] = "default-src 'none'; sandbox"
response.headers['X-Content-Type-Options'] = 'nosniff'
response.headers['X-Frame-Options'] = 'DENY'
response.headers['Referrer-Policy'] = 'no-referrer'

For broader coverage, consider using a Flask after_request handler to set these headers on all file preview responses. If you want to be selective (e.g., only for HTML, SVG, XML), check the Content-Type before setting the headers.

There is precedent in the project for disabling HTML preview due to XSS risk, and sandboxed iframes have been discussed as an additional mitigation (discussion). However, adding these headers is a strong first step.

Actionable next steps: update the relevant Flask endpoints to include these headers, test with malicious HTML/SVG/XML files, and verify that browsers block script execution and unsafe rendering.

To reply, just mention @dosu.

How did I do? Good | Irrelevant | Incorrect | Verbose | Hallucination | Report 🐛 | Other

Chat with Dosu Open in Cursor Join Discord Share on X

@dosubot[bot] commented on GitHub (Nov 28, 2025): <!-- Answer --> To mitigate XSS in file previews, you should add security headers to the Flask Response objects in the preview endpoints. The most effective headers are: - `Content-Security-Policy` (CSP): Restricts what scripts and resources can run. For file previews, a safe default is `Content-Security-Policy: default-src 'none'; sandbox`. - `X-Content-Type-Options: nosniff`: Prevents browsers from interpreting files as a different MIME type, which is critical for SVG/HTML/XML. - `X-Frame-Options: DENY`: Prevents the file from being embedded in an iframe, blocking clickjacking and some XSS vectors. - `Referrer-Policy: no-referrer`: Reduces information leakage. In the Dify codebase, file previews are served in Flask controllers like `api/controllers/files/image_preview.py` and `api/controllers/service_api/app/file_preview.py`. Currently, these endpoints set headers like `Content-Type` and `Content-Disposition` but do not set any security headers ([source](https://github.com/langgenius/dify/blob/a8491c26ea67fbd386a2ca7a5a2b1fa9ba937325/api/controllers/service_api/app/file_preview.py#L26-L186)). You can add these headers directly when constructing the `Response` object, for example: ```python response.headers['Content-Security-Policy'] = "default-src 'none'; sandbox" response.headers['X-Content-Type-Options'] = 'nosniff' response.headers['X-Frame-Options'] = 'DENY' response.headers['Referrer-Policy'] = 'no-referrer' ``` For broader coverage, consider using a Flask `after_request` handler to set these headers on all file preview responses. If you want to be selective (e.g., only for HTML, SVG, XML), check the `Content-Type` before setting the headers. There is precedent in the project for disabling HTML preview due to XSS risk, and sandboxed iframes have been discussed as an additional mitigation ([discussion](https://github.com/langgenius/dify/issues/19159)). However, adding these headers is a strong first step. Actionable next steps: update the relevant Flask endpoints to include these headers, test with malicious HTML/SVG/XML files, and verify that browsers block script execution and unsafe rendering. <!-- Dosu Comment Footer --> *To reply, just mention [@dosu](https://go.dosu.dev/dosubot).* --- <sup>How did I do? [Good](https://app.dosu.dev/response-feedback/155397ae-905a-444b-aa70-dc4d27635a91?feedback_type=great_response) | [Irrelevant](https://app.dosu.dev/response-feedback/155397ae-905a-444b-aa70-dc4d27635a91?feedback_type=irrelevant_answer) | [Incorrect](https://app.dosu.dev/response-feedback/155397ae-905a-444b-aa70-dc4d27635a91?feedback_type=incorrect_sources) | [Verbose](https://app.dosu.dev/response-feedback/155397ae-905a-444b-aa70-dc4d27635a91?feedback_type=too_verbose) | [Hallucination](https://app.dosu.dev/response-feedback/155397ae-905a-444b-aa70-dc4d27635a91?feedback_type=hallucination) | [Report 🐛](https://app.dosu.dev/response-feedback/155397ae-905a-444b-aa70-dc4d27635a91?feedback_type=bug_report) | [Other](https://app.dosu.dev/response-feedback/155397ae-905a-444b-aa70-dc4d27635a91?feedback_type=other)</sup> [![Chat with Dosu](https://dosu.dev/dosu-chat-badge.svg)](https://app.dosu.dev/6088a4f4-073a-43f3-b3d4-4f06fb0c05a0/ask?utm_source=github)&nbsp;[![Open in Cursor](https://dosu.dev/dosu-in-cursor.svg)](https://cursor.com/link/prompt?text=To%20mitigate%20XSS%20in%20file%20previews%2C%20you%20should%20add%20security%20headers%20to%20the%20Flask%20Response%20objects%20in%20the%20preview%20endpoints.%20The%20most%20effective%20headers%20are%3A%0A%0A-%20%60Content-Security-Policy%60%20%28CSP%29%3A%20Restricts%20what%20scripts%20and%20resources%20can%20run.%20For%20file%20previews%2C%20a%20safe%20default%20is%20%60Content-Security-Policy%3A%20default-src%20%27none%27%3B%20sandbox%60.%0A-%20%60X-Content-Type-Options%3A%20nosniff%60%3A%20Prevents%20browsers%20from%20interpreting%20files%20as%20a%20different%20MIME%20type%2C%20which%20is%20critical%20for%20SVG/HTML/XML.%0A-%20%60X-Frame-Options%3A%20DENY%60%3A%20Prevents%20the%20file%20from%20being%20embedded%20in%20an%20iframe%2C%20blocking%20clickjacking%20and%20some%20XSS%20vectors.%0A-%20%60Referrer-Policy%3A%20no-referrer%60%3A%20Reduces%20information%20leakage.%0A%0AIn%20the%20Dify%20codebase%2C%20file%20previews%20are%20served%20in%20Flask%20controllers%20like%20%60api/controllers/files/image_preview.py%60%20and%20%60api/controllers/service_api/app/file_preview.py%60.%20Currently%2C%20these%20endpoints%20set%20headers%20like%20%60Content-Type%60%20and%20%60Content-Disposition%60%20but%20do%20not%20set%20any%20security%20headers%20%28%5Bsource%5D%28https%3A//github.com/langgenius/dify/blob/a8491c26ea67fbd386a2ca7a5a2b1fa9ba937325/api/controllers/service_api/app/file_preview.py%23L26-L186%29%29.%0A%0AYou%20can%20add%20these%20headers%20directly%20when%20constructing%20the%20%60Response%60%20object%2C%20for%20example%3A%0A%0A%60%60%60python%0Aresponse.headers%5B%27Content-Security-Policy%27%5D%20%3D%20%22default-src%20%27none%27%3B%20sandbox%22%0Aresponse.headers%5B%27X-Content-Type-Options%27%5D%20%3D%20%27nosniff%27%0Aresponse.headers%5B%27X-Frame-Options%27%5D%20%3D%20%27DENY%27%0Aresponse.headers%5B%27Referrer-Policy%27%5D%20%3D%20%27no-referrer%27%0A%60%60%60%0A%0AFor%20broader%20coverage%2C%20consider%20using%20a%20Flask%20%60after_request%60%20handler%20to%20set%20these%20headers%20on%20all%20file%20preview%20responses.%20If%20you%20want%20to%20be%20selective%20%28e.g.%2C%20only%20for%20HTML%2C%20SVG%2C%20XML%29%2C%20check%20the%20%60Content-Type%60%20before%20setting%20the%20headers.%0A%0AThere%20is%20precedent%20in%20the%20project%20for%20disabling%20HTML%20preview%20due%20to%20XSS%20risk%2C%20and%20sandboxed%20iframes%20have%20been%20discussed%20as%20an%20additional%20mitigation%20%28%5Bdiscussion%5D%28https%3A//github.com/langgenius/dify/issues/19159%29%29.%20However%2C%20adding%20these%20headers%20is%20a%20strong%20first%20step.%0A%0AActionable%20next%20steps%3A%20update%20the%20relevant%20Flask%20endpoints%20to%20include%20these%20headers%2C%20test%20with%20malicious%20HTML/SVG/XML%20files%2C%20and%20verify%20that%20browsers%20block%20script%20execution%20and%20unsafe%20rendering.)&nbsp;[![Join Discord](https://img.shields.io/badge/join-5865F2?logo=discord&logoColor=white&label=)](https://go.dosu.dev/discord-bot)&nbsp;[![Share on X](https://img.shields.io/badge/X-share-black)](https://twitter.com/intent/tweet?text=%40dosu_ai%20helped%20me%20solve%20this%20issue!&url=https%3A//github.com/langgenius/dify/issues/28909)
Sign in to join this conversation.
No Branch/Tag Specified
Branches Tags
Labels
Clear labels
Knowledge Pipeline
Proposal
WIP
cloud
dependencies
feat:webapp
good first issue
outdated
performance
pull-request
Mirrored from GitHub Pull Request
 python:uv
refactor
size:L
stale
status: accepting prs
status: blocked
status: in discussion
stt & tts
vulnerablity
web
wont-fix
🌊 feat:workflow
🌚 invalid
🐞 bug
👻 feat:rag
💪 enhancement
📚 documentation
🔨 feat:tools
🙋‍♂️ question
🙏 help wanted
🤔 cant-reproduce
🤖 feat:agent
No Label 💪 enhancement
Milestone
No items
No Milestone
Projects
Clear projects
No project
Assignees
Clear assignees
yindo
No Assignees
1 Participants
Notifications
Due Date
No due date set.
Dependencies

No dependencies set.

Reference: langgenius/dify#20673
Delete Branch "%!s()"

Deleting a branch is permanent. Although the deleted branch may continue to exist for a short time before it actually gets removed, it CANNOT be undone in most cases. Continue?