donate hangs my web browser while trying to donate

So i have this weird issue that I can't donate to the tor project, because the donation form completely hangs the tab (and, eventually, the entire web browser), while trying to donate (presumably while trying to solve the ALTCHA).

Here's a video of the phenomenon:

donate-freeze-compressed

On the left, you see the donation site loaded in a window. On the right, the browser console showing the value of navigator.hardwareConcurrency being set to 16.

On the top right, you have a time code reference.

Note that there are other tabs and windows in the background, including this one here where i'm filing this bug, but nothing unusual.

The video starts by me filling up the form with dummy values. But, at about 10 seconds in, i try to click on the country, and nothing happens. The window is still somewhat responsive, i can scroll it up and down, but no UI element is clickable. Notice, at 14 seconds, that the ALTCHA spinner is hung. Also notice the ALTCHA challenge being fetched at 4 seconds, which in itself is now enough to trigger the hang.

This is reproducible in a temporary Firefox profile with only two extensions (ublock origin, unconfigured, and browserpass), started with this command, or even a fully empty profile (firefox --profile $(mktemp -p "${XDG_RUNTIME_DIR:-/tmp}" -d firefox-tmp.XXXXXXXXXX) --no-remote).

Note that the latter, when hanging, says this on the console:

anarcat@angela:Downloads$ firefox --prof$(mktemp -p "${XDG_RUNTIME_DIR:-/tmp}" -d firefox-tmp.XXXXXXXXXX) --no-remote
[1848070, Main Thread] WARNING: Error creating proxy: Error calling StartServiceByName for org.gtk.vfs.Daemon: Unit gvfs-daemon.service is masked. (g-io-error-quark, 36)
: 'glib warning', file ./toolkit/xre/nsSigHandlers.cpp:167

(Firefox-esr:1848070): GVFS-WARNING **: 10:31:39.605: Error creating proxy: Error calling StartServiceByName for org.gtk.vfs.Daemon: Unit gvfs-daemon.service is masked. (g-io-error-quark, 36)

out of memory: 0x0000000000000038 bytes requested
out of memory: 0x0000000000000038 bytes requested
out of memory: 0x0000000000000038 bytes requested
out of memory: 0x0000000000000038 bytes requested
out of memory: 0x0000000000000038 bytes requested
out of memory: 0x0000000000000038 bytes requested
out of memory: 0x0000000000000038 bytes requested
out of memory: 0x0000000000000038 bytes requested
out of memory: 0x0000000000000038 bytes requested
out of memory: 0x0000000000000038 bytes requested
out of memory: 0x0000000000000038 bytes requested
out of memory: 0x0000000000000038 bytes requested
out of memory: 0x0000000000000038 bytes requested
out of memory: 0x0000000000000038 bytes requested
out of memory: 0x0000000000000038 bytes requested
out of memory: 0x0000000000000038 bytes requested
out of memory: 0x0000000000000080 bytes requested
out of memory: 0x0000000000000078 bytes requested
out of memory: 0x0000000000000078 bytes requested

This is also reproducible with both plugins disabled, in that case the entire browser crashes (yep), with Exiting due to channel error..

I am running Firefox 115.15.0esr, on Debian 12 stable ("bookworm") with a Linux 6.10.6-1~bpo12+1 kernel, under a Sway desktop environment. My laptop is a Framework 12th gen laptop, see the specifications of my build, although I'm now at 32GiB of RAM.

I have not tried reproducing under KDE or GNOME, but am happy to. Same with Tor browser.

Now, of course, browsers shouldn't hang like this. This is clearly a bug somewhere in Firefox or below the stack.

Yet, I can't donate, so ... uh... this feels like a problem we should fix anyways.