Including: (1) <h1> title, (2) <title> title, (3) edit summary.

Non-executable HTML tags are also affected in (1) and (2) above, see:

https://test.wikidata.org/w/index.php?title=Q143&action=history

Thanks to the standard sanitizer applied to page titles, executable tags are filtered out:

https://test.wikidata.org/w/index.php?title=Q144&action=history

I think this has been fixed in the mean time.

(In reply to Bene* from comment #3)

I think this has been fixed in the mean time.

No. Have a look at the linked page: edit summary of the first revision says "Created a new item: 1 & 2" but the heading is "Revision history of "1 &amp; 2" (Q142)". Obviously they don't match: either one side overescaped the label once, or another side failed to do an escape.

Hmm I should try a new item as existing summaries are not dynamically generated, but the result is the same: https://test.wikidata.org/w/index.php?title=Q785&action=history

Oh, I was referring to your comment #1

Including: (1) <h1> title, (2) <title> title, (3) edit summary.

Only the edit summary still has issues which I didn't notice.

In T56153#9666401, @Pppery wrote:

Boldly closing as resolved since this appears to have been fixed at some point.

https://test.wikidata.org/w/index.php?title=Q142&action=history shows "1 & 2' in both places. Ditto https://test.wikidata.org/w/index.php?title=Q785&action=history

Shouldn't it display 1 &amp; 2, though?