On any Jira issue, click the External Share tab on the activities panel.
Once you've created your link and selected the options you require (see Link Options for more details). You can also send the link directly via email.
You can customize the format of your email, decide if you want to share the password, and add a friendly message
Click the External Share button in the left menu to see all links that have been created in Project.
You can create here External Share Filter and External Share Board.
External Share Board
External Share Filter
The shared issue displays the issue summary, description, Status, Assignee, Reporter and Components by default. In the Project Settings, you can manage shared fields.
The External User will be able to add comments and attachments or change issues status if those options have been enabled in link options!