Activity Stream RSS feeds do not validate when tested with feed validators like WSC's Feed Validation Service

Problem Definition

JIRA's Activity Stream RSS feeds do not validate when tested with feed validators like WSC's Feed Validation Service on https://validator.w3.org/feed/ or https://validator.w3.org/feed/#validate_by_input for instance. A few lines of the XML content report errors.

The problem with the lack of validation is that the feed may be rejected on third-party services where a user may need to use them.

Suggested Solution

Fix the errors reported with the Feed Validation:

Workaround

There is no known workaround.