Hanging the browser with combination of specific extensions and specific website

[UCyborg]

I've been bothered by random unexplainable hangs of the browser for quite some time now. Finally, I found the way to consistently reproduce it. While I'm not sure if the cause between reproducible and random cases is actually the same, the final result sure looks like it. For this, a specific external application is needed along with specific two browser extensions, one extension has to be configured to work with the external application. Pale Moon is assumed to be configured with default settings and no extensions, as starting from fresh profile.

External prerequisites:

KeePass
KeePassHttp plugin (you need to download KeePassHttp.plgx directly from the repo's root folder, it's not under Releases, so clicking KeePassHttp.plgx, then View raw to trigger the download)

You can use either installer or portable version of KeePass. Regardless of the option you choose, the most important step is to put the *.plgx file from above link inside Plugins subfolder of the folder where you have installed / extracted KeePass.

Launch KeePass, first time launch after seeing the plugin, it will briefly show compiling and loading plugins window.

Go to File->New... and follow on-screen instructions to create an empty password database. It suffices to specify the password, confirm, no need to print emergency page or change any settings in the window that opens in the end, just confirm defaults with OK.

Now onto Pale Moon prerequisites:

uBlock Origin
PassIMoon or PassIFox (pick only one)

uBlock doesn't need specific configuration, just has to be enabled. As for the other, after installing and restarting the browser, while KeePass should still be running with opened newly created database, go to any website with login form, the extension should prompt to connect to KeePass with notification below tab bar. Click Connect..., after which you will be prompted to specify the name that will identify connection between Pale Moon and KeePass, type any name you like and confirm.

This is all when it comes to the prerequisites, now onto triggering the bug. Go to https://ekomunala.ibled.si/, which should re-direct to login form. Enter any made up user name and password and click SIGN IN or confirm with Enter key. At this point, the browser should become unusable.

Now awaiting what wise developers have to say about this issue.

[UCyborg]

Hm, happens on my home desktop, both on Windows 10 20H2 and Linux (KUbuntu 21.10), SSE2 version. No issue on work laptop, both AVX and SSE2 version.

The notable hardware differences, home desktop has AMD Phenom II X4 920 and NVIDIA GeForce GTX 750 Ti, work laptop has Intel Core i7-6700HQ and Intel HD Graphics 530 + NVIDIA GeForce GTX 950M (the latter being selected to be used for Pale Moon). No idea what to look for.

[UCyborg]

I think I got in at work because I was in private tab. That or turning off Remember passwords gets me in at home.

[Moonchild]

since the behaviour changes based on password manager settings and the prerequisite is a password extension then I'd say your having an extension compatibility issue.

[UCyborg]

Something's fishy; so far, I only encountered it on this specific site. And all 4 factors must apply for it to be consistently reproducible (goes for my work laptop too):

• This specific URL
• uBlock Origin extension enabled (the issue happens even if ekomunala.ibled.si is completely excluded from filtering)
• PassIFox / PassIMoon extension enabled and connected to KeePass
• signon.rememberSignons enabled

I hoped someone would have a look at what happens in the browser for its UI to hang as it's very specific, otherwise, hangs would happen on every site with login forms and these extensions.

I was curious to see if it would happen on SeaMonkey as well, buuut that browser currently can't stomach the JavaScript on that site. 🙃

[UCyborg]

I set a breakpoint on literally every function in PassIFox (first statement of the function, of course). And none gets hit when I click login button on the site. 🙃