Using a reference with formulas inside of a figure caption, breaks the generated HTML

[leoschwarz]

Dear developers,
The second plot is rendered correctly whereas the first one is messed up unless you add a fig.alt since the unescaped HTML of the formula ends up in the aria-label tag of the <img> element.

---
title: "Circle Plot"
output:
  bookdown::html_document2:
    toc: yes
    toc_depth: 2
---

(ref:caption) The formula for a circle: $x^2 + y^2 = r^2$).

```{r circle-plot, fig.cap="(ref:caption)"}
t <- seq(0, 2*pi, length.out = 1000)
x <- cos(t)
y <- sin(t)

plot(x, y, type = "l", asp = 1, xlab = "x", ylab = "y", main = "Circle")
```

```{r circle-plot2, fig.cap="The formula for a circle: $x^2 + y^2 = r^2$."}
plot(x, y, type = "l", asp = 1, xlab = "x", ylab = "y", main = "Circle")
```

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• formatted your issue so it is easier for us to read?

• included a minimal, self-contained, and reproducible example?

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R version 4.4.1 (2024-06-14)
Platform: aarch64-apple-darwin23.4.0
Running under: macOS Sonoma 14.5

Locale: de_CH / UTF-8 / de_CH / C / de_CH / de_CH

Package version:
  base64enc_0.1.3   bookdown_0.40.1   bslib_0.8.0       cachem_1.1.0
  cli_3.6.3         digest_0.6.36     evaluate_0.24.0   fastmap_1.2.0
  fontawesome_0.5.2 fs_1.6.4          glue_1.7.0        graphics_4.4.1
  grDevices_4.4.1   highr_0.11        htmltools_0.5.8.1 jquerylib_0.1.4
  jsonlite_1.8.8    knitr_1.48        lifecycle_1.0.4   memoise_2.0.1
  methods_4.4.1     mime_0.12         R6_2.5.1          rappdirs_0.3.3
  rlang_1.1.4       rmarkdown_2.27    sass_0.4.9        stats_4.4.1
  tinytex_0.52      tools_4.4.1       utils_4.4.1       xfun_0.46
  yaml_2.3.10