netbox-data-flows has stored XSS in ObjectAlias names rendered inside DataFlow tables

Summary

An authenticated user who can create or edit ObjectAlias objects can store arbitrary HTML/JavaScript in an alias name. That payload is later rendered unescaped in DataFlow table views, causing a stored XSS when another user views the affected page.

Details

The issue is caused by unsafe HTML generation in the plugin’s custom table column renderer.

Relevant code on main (bf96eac, same commit as origin/main at the time of review):

• netbox_data_flows/models/objectaliases.py
  • ObjectAlias.name is user-controlled (CharField)
  • ObjectAlias.__str__() returns self.name directly
• netbox_data_flows/tables/dataflows.py
  • DataFlowTable.sources and DataFlowTable.destinations use ObjectAliasListColumn
• netbox_data_flows/tables/columns.py
  • ObjectAliasListColumn.render() calls object_list_to_string(value.all(), linkify=True)
• netbox_data_flows/utils/helpers.py
  • object_list_to_string() builds raw anchor tags with:
    python

    mark_safe(separator.join(f'<a href="{o.get_absolute_url()}">{o}</a>' for o in objects))

The alias text ({o}) is inserted into HTML without escaping, then the whole string is marked safe. Because ObjectAlias.__str__() returns the user-supplied name, HTML/JS in the alias name is executed in the victim’s browser.

This affects any page rendering DataFlowTable, including at least:

• the main Data Flow list page
• model tabs that reuse DataFlowTable

PoC

Environment:

• NetBox with netbox-data-flows installed
• No special plugin configuration required

Steps:

1. Log in as a user with permission to create or edit ObjectAlias and DataFlow.
2. Create a new ObjectAlias with the following name:
   html

   <img src=x onerror=alert(document.domain)>

3. Create or edit a DataFlow so this alias is present in either sources or destinations.
4. Log in as another user and open the Data Flow list page in the plugin UI.
5. The JavaScript executes when the table renders the alias list.

A simple path to trigger is the Data Flow list page. Any other page that renders DataFlowTable should also be tested.

Impact

This is a stored cross-site scripting vulnerability.

Impacted users:

• any authenticated user who can view a page rendering the affected DataFlow table
• especially higher-privileged NetBox users, because an attacker with lower privileges may target them by planting a malicious alias name

Possible impact:

• session theft
• execution of privileged actions in the victim’s session
• exfiltration of data visible to the victim in NetBox