Headline
GHSA-wpq5-3366-mqw4: Label Studio allows Cross-Site Scripting (XSS) via GET request to `/projects/upload-example` endpoint
Description
Label Studio’s /projects/upload-example endpoint allows injection of arbitrary HTML through a GET request with an appropriately crafted label_config query parameter. By crafting a specially formatted XML label config with inline task data containing malicious HTML/JavaScript, an attacker can achieve Cross-Site Scripting (XSS). While the application has a Content Security Policy (CSP), it is only set in report-only mode, making it ineffective at preventing script execution.
The vulnerability exists because the upload-example endpoint renders user-provided HTML content without proper sanitization on a GET request. This allows attackers to inject and execute arbitrary JavaScript in victims’ browsers by getting them to visit a maliciously crafted URL.
This is considered vulnerable because it enables attackers to execute JavaScript in victims’ contexts, potentially allowing theft of sensitive data, session hijacking, or other malicious actions.
Steps to reproduce
- Create a malicious label config that includes an XSS payload in embedded task data:
<View><!-- {"data": {"text": "<div><img src=x
onerror=eval(atob(`YWxlcnQoIlhTUyIp`))></div>"}} --><HyperText name="text"
value="$text"/></View>
- URL encode the payload and access the following URL:
- http://app/projects/upload-example/?label_config=%3CView%3E%3C!–%20{%22data%22:%20{%22text%22:%20%22%3Cdiv%3E%3Cimg%20src=x%20onerror=eval(atob(
YWxlcnQoIlhTUyIp))%3E%3C/div%3E%22}}%20–%3E%3CHyperText%20name=%22text%22%20value=%22$text%22/%3E%3C/View%3E
When executed, the payload causes the application to render an HTML page containing an img tag that fails to load, triggering the onerror event handler which executes base64-decoded JavaScript, demonstrating successful XSS execution in the victim’s browser.
Mitigations
- Enable the Content Security Policy in enforcement mode instead of report-only mode to actively block unauthorized script execution
- Deprecate the
GETbehavior at theexample-configendpoint since it’s not used
Impact
The vulnerability requires no special privileges and can be exploited by getting a victim to visit a crafted URL. The impact is high as it allows arbitrary JavaScript execution in victims’ browsers, potentially exposing sensitive data or enabling account takeover through session theft.
- GitHub Advisory Database
- GitHub Reviewed
- CVE-2025-25296
Label Studio allows Cross-Site Scripting (XSS) via GET request to `/projects/upload-example` endpoint
Moderate severity GitHub Reviewed Published Feb 14, 2025 in HumanSignal/label-studio • Updated Feb 14, 2025
Package
pip label-studio (pip)
Affected versions
< 1.16.0
Description
Label Studio’s /projects/upload-example endpoint allows injection of arbitrary HTML through a GET request with an appropriately crafted label_config query parameter. By crafting a specially formatted XML label config with inline task data containing malicious HTML/JavaScript, an attacker can achieve Cross-Site Scripting (XSS). While the application has a Content Security Policy (CSP), it is only set in report-only mode, making it ineffective at preventing script execution.
The vulnerability exists because the upload-example endpoint renders user-provided HTML content without proper sanitization on a GET request. This allows attackers to inject and execute arbitrary JavaScript in victims’ browsers by getting them to visit a maliciously crafted URL.
This is considered vulnerable because it enables attackers to execute JavaScript in victims’ contexts, potentially allowing theft of sensitive data, session hijacking, or other malicious actions.
Steps to reproduce
- Create a malicious label config that includes an XSS payload in embedded task data:
<View><!-- {"data": {"text": “<div><img src=x onerror=eval(atob(`YWxlcnQoIlhTUyIp`))></div>"}} --><HyperText name="text” value="$text"/></View>
- URL encode the payload and access the following URL:
- http://app/projects/upload-example/?label_config=%3CView%3E%3C!–%20{%22data%22:%20{%22text%22:%20%22%3Cdiv%3E%3Cimg%20src=x%20onerror=eval(atob(`YWxlcnQoIlhTUyIp`))%3E%3C/div%3E%22}}%20–%3E%3CHyperText%20name=%22text%22%20value=%22$text%22/%3E%3C/View%3E
When executed, the payload causes the application to render an HTML page containing an img tag that fails to load, triggering the onerror event handler which executes base64-decoded JavaScript, demonstrating successful XSS execution in the victim’s browser.
Mitigations
- Enable the Content Security Policy in enforcement mode instead of report-only mode to actively block unauthorized script execution
- Deprecate the GET behavior at the example-config endpoint since it’s not used
Impact
The vulnerability requires no special privileges and can be exploited by getting a victim to visit a crafted URL. The impact is high as it allows arbitrary JavaScript execution in victims’ browsers, potentially exposing sensitive data or enabling account takeover through session theft.
References
- GHSA-wpq5-3366-mqw4
- HumanSignal/label-studio@8cf6958
Published to the GitHub Advisory Database
Feb 14, 2025
Last updated
Feb 14, 2025