TYPO3 Core

Since 10.1 this should not be the case anymore as this features adds automatically these attributes:
https://docs.typo3.org/c/typo3/cms-core/master/en-us/Changelog/10.1/Feature-78488-AddRelNoreferrerToExternalLinks.html

Georg Ringer wrote:

how do you generate your menu?

I use standard Bootstrap_Package (newest version) but I also wrote to Richard Haeser and some of the Bootstrap_package guys, they use a extension for solving this problem, but seems for them it also does not work out of box.
All external Links (generated by menu OR manual) should have this, no matter how they have been implemented.
But the links are (like shown in the "external Link.PNG") external Links as a Menu-Point:
So they are rendered as a menu in the Navigation

All FLUID Menu* templates are generated as normal html a-tag and there is missing the noopener condition - something like:

// missing: {f:if(condition: '{page.data.doktype} == 3', then: 'rel="noopener"')}

<a href="{page.link}"{f:if(condition: page.target, then: ' target="{page.target}"')} title="{page.title}" {f:if(condition: '{page.data.doktype} == 3', then: 'rel="noopener"')}>

Please see issue #95051 and let's continue there...

Relevant aspect, see https://forge.typo3.org/issues/95051#note-7

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