src/vs/workbench/services/extensionManagement/browser/webExtensionsScannerService.ts/WebExtensionsScannerService/readSystemExtensions
class WebExtensionsScannerService:	private async readSystemExtensions(): Promise<IExtension[]> {
		const systemExtensions = await this.builtinExtensionsScannerService.scanBuiltinExtensions();
		const cachedSystemExtensions = await Promise.all((await this.readSystemExtensionsCache()).map(e => this.toScannedExtension(e, true, ExtensionType.System)));

		const result = new Map<string, IExtension>();
		for (const extension of [...systemExtensions, ...cachedSystemExtensions]) {
			const existing = result.get(extension.identifier.id.toLowerCase());
			if (existing) {
				// Incase there are duplicates always take the latest version
				if (semver.gt(existing.manifest.version, extension.manifest.version)) {
					continue;
				}
			}
			result.set(extension.identifier.id.toLowerCase(), extension);
		}
		return [...result.values()];
	}