Relative links in description markup broken

Q&A

• OS: n/a (linux)
• Browser: n/a (chrome)
• Version: n/a (87.0.4280.66)
• Method of installation: n/a (maven WebJars artifact: org.webjars:swagger-ui🫙3.35.0)
• Swagger-UI version: 3.35.0
• Swagger/OpenAPI version: OpenAPI 3.0.1

Content & configuration

Example Swagger/OpenAPI definition:

openapi: 3.0.1
info:
  title: Test API
  version: 0.0.1
  description: General info can be found in [readme-api.html](readme-api.html).
servers:
- url: https://prod.example.com/test/v1
  description: Default Server
paths:
  /status:
    get:
      summary: Service status
      responses:
        "200":
          description: Service is ready
        "404":
          description: Service is not ready

Swagger-UI configuration options:

SwaggerUI({
    /*--------------------------------------------*\
     * Core
    \*--------------------------------------------*/
    configUrl: null,
    dom_id: "#swagger-ui",
    dom_node: null,
    spec: {},
    url: "",
    urls: [{
      name: "Test API",
      url: "http://doc.example.com/apis/testApi/service-api.yaml"
    }],
    /*--------------------------------------------*\
     * Plugin system
    \*--------------------------------------------*/
    layout: "StandaloneLayout",
    plugins: [
      SwaggerUIBundle.plugins.DownloadUrl,
    ],
    presets: [
      SwaggerUIBundle.presets.apis,
      SwaggerUIStandalonePreset
    ],
    /*--------------------------------------------*\
     * Display
    \*--------------------------------------------*/
    deepLinking: true,
    displayOperationId: false,
    defaultModelsExpandDepth: 1,
    defaultModelExpandDepth: 1,
    defaultModelRendering: "example",
    displayRequestDuration: false,
    docExpansion: "none",
    filter: false,
    maxDisplayedTags: null,
    operationsSorter: "alpha",
    showExtensions: false,
    showCommonExtensions: false,
    tagSorter: "alpha",
    /*--------------------------------------------*\
     * Network
    \*--------------------------------------------*/
    oauth2RedirectUrl: null,
    validatorUrl: null,
    /*--------------------------------------------*\
     * Macros
    \*--------------------------------------------*/
    modelPropertyMacro: null,
    parameterMacro: null
})

Describe the bug you're encountering

Relative links in description fields throughout the spec are treated as relative to the URL form which the Swagger UI was loaded rather than the URL from which the spec was loaded.

Steps to reproduce the behavior

1. Configure Swagger UI as described above, update the spec URL as needed.
2. Load the Swagger UI and inspect the target of the readme-api.html link in the API description.

Expected behavior

The link is assumed to be relative to the URL the spec (in which it is defined) was loaded from. I.e. in the case presented in the screenshots, the link target should be: http://doc.example.com/apis/testApi/readme-api.html.

Screenshots

1. The URL from which spec was loaded (and which should be used as the base URL for any relative links in the various description fields throughout the spec):
   

2. The URL from which the Swagger UI was loaded (and which is currently used as the base URL for the relative links in the descriptions):
   

Start by reproducing the issue with the provided OpenAPI definition, Swagger UI configuration, and external spec URL, then trace how description links are rendered and how their base URL is selected. Confirm that relative links resolve against the loaded spec URL rather than the Swagger UI page URL, and verify the expected target with the reproduction case.