How to sanitize and validate user input to pass a Checkmarx scan

Question

I have an endpoint that receives a String from the client as seen below:

@GET
@Path("/{x}")
public Response doSomething(@PathParam("x") String x) {
    String y = myService.process(x);
    return Response.status(OK).entity(y).build();
}

Checkmarx complains that this element’s value then "flows through the code without being properly sanitized or validated and is eventually displayed to the user in method doSomething"

Then I tried this:

@GET
@Path("/{x}")
public Response doSomething(@PathParam("x") String x) {
    if (StringUtils.trimToNull(x) == null || x.length() > 100) { 
        throw new RuntimeException(); 
    }
    x = x.replace("'", "").replace("`", "").replace("\\", "").replace("\"", "")
    String y = myService.process(x);
    y = y.replace("'", "").replace("`", "").replace("\\", "").replace("\"", "")
    return Response.status(OK).entity(y).build();
}

But it still considers this a high severity vulnerability.

How do I properly sanitize or validate to pass a Checkmarx scan?

Answer 1

HtmlUtils from spring-web got the job done with:

HtmlUtils.htmlEscape(x)

Maven dependency:

<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-web</artifactId>
    <version>5.1.7.RELEASE</version>
</dependency>

Answer 2

in .Net framework > 4.0 use AntiXSS

AntiXssEncoder.HtmlEncode()