[SLING-7777] XSSFilter is rejecting URLs containing only queries or fragments

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: XSS Protection API 2.0.10
• Fix Version/s: XSS Protection API 2.0.12
• Component/s: XSS Protection API
• Labels: XSS
• Assignee: Radu Cotescu
• Reporter: Lars Krapf
• Created: 12/Jul/18 13:46
• Updated: 07/Aug/18 12:20
• Resolved: 02/Aug/18 15:21

Description

The XSSFilter is erroneously rejecting URLs that consist only of queries, (potentially empty) fragments or both, e.g. "#", "#test", "?foo=bar" etc. 

Even though the RELATIVE_PART regexp contains an PATH_EMPTY group, it is explicitly matching the entire string, so will fail if the QUERY or FRAGMENT groups match.

A potential solution (see attached patch and tests) might be to remove the PATH_EMPTY group from the RELATIVE_PART, and make the entire RELATIVE_PART optional by adding ? to the group in RELATIVE_REF. This will still match completely empty URLs.