CKEditor 5 moves some classes in the a tag

I can't seem to reproduce this. Please add the complete steps to reproduce to the issue summary. Using a site like https://simplytest.me is a way to create a clean Drupal site for bug reproduction.

Also, see if you can reproduce the bug with the CKEditor 5 demo so we can understand if this is CKEditor or a Drupal filter causing it.

1. https://simplytest.me/ does not work: There was a build error 60%
2. CKEditor 5 demo: the problem does not reproduce.
3. I create the page https://prova.gmpe.it/tettonica/attivita-sismica-vulcanica
4. In the source code I insert:

<p class="text-align-center">
<a class="glightbox" href="/sites/default/files/tettonica/tectonics_map.gif"><img src="/sites/default/files/tettonica/vulcani.png" width="651" height="223"></a>
</p>

5. I save.
6. I check the source code:

<p class="text-align-center">
<a href="/sites/default/files/tectonica/tectonics_map.gif"><img class="glightbox" src="/sites/default/files/tectonica/vulcani.png" width="651" height="223"></a>
</p>

7. The problem occurs in all pages with the glightbox class
8. In text formats there are no filters for glightbox

I continue not to be able to reproduce this bug. Here is what it did:

1. Installed a new Drupal 11 site.
2. Added an article.
3. For the body field I selected Text Format: Full HTML.
4. I switched the editor to source mode.
5. I pasted the HTML given in the issue summary.
6. I saved the node.
7. I examined the HTML. There are no changes.
8. I edited the node.
9. I switched the editor to source mode.
10. I examined the HTML. There are no changes.

Because you have a site that can reproduce the bug we need much more detail about how CKEditor and the text formats are configured.

Attached are the images of the buttons and filters, unfortunately in Italian, of full_html.

Instead of modifying the existing pages, I repeat the procedure on a new page: https://prova.gmpe.it/prove.

1. I insert an image with IMCE
2. I connect the image with another image
3. In the link I put the glightbox class
4. I save and check if it works: html has not changed
5. In the same page I copy the code of another page that originally had colorbox
6. I replace colorbox with glightbox
7. I save and check if it works: html has changed, the class has been moved from the link to the image

In the same page I have two images, one works and the other does not. Absurd!
Practically, it only works on new images and not on existing ones.
Unfortunately I have to replace all the colorbox in the site with glightbox because Colorbox Inline module it looks like it won't be there for drupal 11.

Thanks for your patience

I found the problem: it's the p tag

It works if I put:

<a class="glightbox" href="/sites/default/files/tettonica/tectonics_map.gif"><img src="/sites/default/files/tettonica/vulcani.png" data-entity-uuid="" data-entity-type="file" alt="distribuzione di vulcani e terremoti" width="651" height="223"></a>

If instead I put:

<p class="text-align-center">
<a class="glightbox" href="/sites/default/files/tettonica/tectonics_map.gif"><img src="/sites/default/files/tettonica/vulcani.png" data-entity-uuid="" data-entity-type="file" alt="distribuzione di vulcani e terremoti" width="651" height="223"></a>
</p>

CKEditor moves the class and shows the wrong image:

<p class="text-align-center">
<a href="/sites/default/files/tettonica/tectonics_map.gif"><img class="glightbox" src="/sites/default/files/tettonica/vulcani.png" data-entity-uuid="" data-entity-type="file" alt="distribuzione di vulcani e terremoti" width="651" height="223"></a>
</p>

Unfortunately without the p tag I don't know how to center the images.

Thanks and best regards

I found a way to center the images, so the problem is circumvented by avoiding putting the p and div tags.

Kind regards