rel="noopener" prevents the new page from being able to access the window.opener property and ensures it runs in a separate process.
rel="noreferrer" attribute has the same effect, but also prevents the Referer header from being sent to the new page. See Link type "noreferrer".

Huh. Okay, so it should also work. Thanks for clearing that out.

The question originated from trying to get my site to perform better in google LightHouse test.
It gives the warning to add rel="noopener" or rel="noreferer" to the link. After adding rel="noreferer", the warning remains. While in other links (from custom html) the warning disappeared after adding rel="noopener".

But I guess this is an issue for LightHouse than, and not Joomla :)

I actually copy pasted that information from lighthouse :)

Set to "closed" on behalf of @jwaisner by The JTracker Application at issues.joomla.org/joomla-cms/27990

Closing at this has been identified as not being related to Joomla!.

I'dd like to reopen this. After thinking some more on it ...
There are some cases where rel="noopener" is the only good option.
Because we don't want to lose the Referer header, rel="noreferer" just wont do.

Set to "open" on behalf of @jwaisner by The JTracker Application at issues.joomla.org/joomla-cms/27990

Reopened as per Author's request and new information provided.

See #24337 for J4 and per the discussion it will not be fixed for J3. This should be closed and continue the discussion in the other issue.

I don't think it's the same issue. I don't mean to enforce this on all external url's.
It's just an option that's missing in the dropdown list for foreign URL menu type, in /administrator/components/com_menus/models/forms/item_url.xml.

For the field "menu-anchor_rel" (list type) this option should be added:
<option value="noopener"/>

That's all

@TVBZ Got it. Please test PR #28005. Thanks.