This issue seems to be related to Kozea/WeasyPrint#2082

Created Kozea/WeasyPrint#2325 for this.

WeasyPrint v64.0 fixes this issue.
Above document generated with the new version: https://t4.fq.nz/xml2rfc.1215/rfc9553.pdf

In https://t4.fq.nz/xml2rfc.1215/rfc9553.pdf, searching for terms causes a vertical green bar (in Preview 11), which is the width of the search term and the length of the page, to appear wherever the term is. In Acrobat Reader, the bars are blue and not quite as long (about half a page).

I don't see a green line (macOS 15.3).
Do you have a screenshot?

Ah, it's blue and on Page 50 (after searching).

And it is a link to [email protected] ?

Can reproduce - Preview 11.0 on macOS 15.1.1:

I edited my comment above. I was able to reproduce both in Preview and in Acrobat Reader.

Similar weird things happen in Nitro PDF, which AFAIK does not use Apple's PDF engine.

Weird. I can't see this on macOS preview or on Firefox. I'll investigate this next week.

What we see is that highlight boxes (like those used for searching and marking hyperlinks) appear to have near-infinite vertical size. That causes the highlight boxes to appear as vertical lines (boxes, actually). If you don't search or have a page with marked hyperlinks you can't see that effect.

(I don't see it in Firefox either.)

It's a bug in WeasyPrint, which has been fixed¹.
Let's wait till next version.