Custom Branding: Relative URL should be allowed

CHANGELOG.md

@@ -22,6 +22,7 @@ Inspired from [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 - [Workspace] Setup workspace skeleton and implement basic CRUD API ([#5075](https://github.com/opensearch-project/OpenSearch-Dashboards/pull/5075))
 - [Decouple] Add new cross compatibility check core service which export functionality for plugins to verify if their OpenSearch plugin counterpart is installed on the cluster or has incompatible version to configure the plugin behavior([#4710](https://github.com/opensearch-project/OpenSearch-Dashboards/pull/4710))
 - [Discover] Display inner properties in the left navigation bar [#5429](https://github.com/opensearch-project/OpenSearch-Dashboards/pull/5429)
+- [Custom Branding] Relative URL should be allowed for logos ([#5572](https://github.com/opensearch-project/OpenSearch-Dashboards/pull/5572))
 
 ### 🐛 Bug Fixes
 

src/core/server/rendering/rendering_service.test.ts

@@ -195,6 +195,11 @@ describe('RenderingService', () => {
       const result = await service.isUrlValid('/', 'config');
       expect(result).toEqual(false);
     });
+
+    it('checks relative URL returns true', async () => {
+      const result = await service.isUrlValid('/demo/opensearch_mark_default.png', 'config');
+      expect(result).toEqual(true);
+    });
   });
 
   describe('isTitleValid()', () => {

src/core/server/rendering/rendering_service.tsx

@@ -371,6 +371,9 @@ export class RenderingService {
       this.logger.get('branding').error(`${configName} config is invalid. Using default branding.`);
       return false;
     }
+    if (url.startsWith('/')) {
+      return true;
+    }
     return await Axios.get(url, {
       httpsAgent: this.httpsAgent,
       adapter: 'http',