Validator badge misses host in path to json spec

Description

I compiled the validator-badge project to a war file and started it in a jetty instance on port 9091. I modified file \modules\swagger-generator\src\main\webpp\index.htm, I added the line validatorUrl: "http://localhost:9091", in the call to const ui = SwaggerUIBundle. I compiled swagger-codegen and started the war in a jetty container on port 9090. Now, I call the swagger-ui in the browser and the validator badge for the sample /api/swagger.json is red.
It is called by http://localhost:9091/?url=/api/swagger.json It seems to miss a host name in the path to the json file.
If I enter the full path http://localhost:9090/api/swagger.json into the text field and click Explore the host is cut off and I am being redirected to the page I've been before.
When I call the validator in the browser and include the host name in the URL param like http://localhost:9091/?url=http://localhost:9090/api/swagger.json I get the green badge as expected.

Is it not allowed to enter a host name in the text field? How to pass a json specification including host name?

Command line used for generation

I compiled validator-badge and codegen using this mvn call from latest head
mvn clean package -DskipTests -Dmaven.test.skip=true
I generated the files swagger-validator-1.0.5-SNAPSHOT.war and swagger-generator-2.2.3-SNAPSHOT.war

My working copy of validator is on commit c7c2d84c4aa3fe798e1dcee213fc542b920148e2
codegen commit f14d8067c45554ab7fed4d214b459a177f8b1217

Start with modules/swagger-generator/src/main/webpp/index.htm and the SwaggerUIBundle validatorUrl configuration. Reproduce the validator badge and Explore behavior using the two Jetty WARs and the sample /api/swagger.json, then trace how the validator URL parameter is handled. Done means a specification URL containing a host is preserved and produces the expected green badge.