MAL randomly downloading .htm files?

Problem: Firefox downloading .htm files while browsing MAL.
It seems to be a Firefox specific problem with the website, having to do with the way it handles ads and user privacy. A quick google shows it has happened to users on other websites, and at least two mentioned were anime/video game websites. Could be a common ad server?

Disclaimer: I'm not a web developer, just a hobbyist! I have no idea what I'm talking about.

Firefox downloads several .htm files at once (automatic downloads turned on for testing) eg.

How to reproduce it:

1. Visit and click through individual entries on MAL. Quicker clicks (before full page load) seems to replicate it more easily.
   
2. Wait until several 0 byte .htm files download.
   

Things I did to try and figure out the problem:

Turning off javascript stopped it from happening, but that also breaks half the site. The fact that it doesn't happen on every single page click lines up with it being a part of ads being served on rotation.

tl;dr in case no one wants to read all this:
I don't think there's anything the average user can do, either Firefox changed or MAL has to audit and fix a misconfigured ad (?). But again, I'm not a web developer, so if I'm completely wrong HAHAHA DISREGARD THAT, I SUCK—

I am a web developer and have to agree that your logic is sound, however those 302 errors, type errors and o.setTargetting a function in Google Publisher Tag to target specific ads likely has nothing to do with it, and is most likely an error with onetag-sys.com and its ad delivery/replacement method since that is the html file that is being downloaded.
(you can right click the downloaded file to copy link or open it to view source)
and I know MAL uses google for its ads as well as https://hb.vntsm.com/v3/live/ad-manager.min.js and https://tagmanager.smartadserver.com/3948/394613/smart.prebid.js just to name a few... though I did not find onetag-sys in it's list so not sure which .js file or ad service is loading that ad service...MAL's kinda over killing it with how many they use...

not that it matters since sooner or later onetag's faulty ads or more accurate not compatible with firefox, will be out bid by another ad service, repaired or can be blocked with ad blockers.

I didn't see any posts about this when I first noticed it a few days ago. Now I know it wasn't just me. I've tried changing some about:config settings suggested, but with no luck.

I'm curious what Firefox versions this is an issue with. I am using an outdated version due to an unsupported OS.

@ArcadiaInferno I tested it with the latest stable release at the time (139.0.1) so if you're getting it on an older version too then nothing can be done until the incompatible ad is gone.

I tested it on a fresh copy of Firefox on a machine that had never accessed MAL via Firefox after users from the original thread said it stopped for them.

It's a misconfigured ad delivery service, as discussed upthread, and I'm pretty sure it will happen sporadically (not sure which ad causes it and ads rotate) until that is fixed if it hasn't been already.

I looked into this and it is caused by a misconfigured server often from an unknown MIME type and is actually normal browser behavior. I find posts people describing similar on different sites over a decade ago in various browsers. Clearing your cache might stop it if it was just a temporary thing.



Check Firefox ESR if it is compatible otherwise see if there is a fork that is compatible like Librewolf or Palemoon. If it is a really old OS sometimes people make specific forks for that system as a backport.


Set download location to always ask. If it was malware, which it isn't you'd see the issue of unprompted downloads.

that's correct, as in it's one of the possible causes, the files for me were not empty, but like 5-8kb and if you edit them, you can clearly see they are HTML files that have a Javascript wrapper for a video ad banner, so if their video type or code isn't compatible with Firefox it may download instead, but that's just one possibility..

and yea they would have to fix it then you clear your cache and it's done, but as you said that's if it's a temporary thing ie someone reports it to them and as I pointed out here https://myanimelist.net/forum/?goto=post&topicid=2217986&id=72843115 in the Show Image spoiler, we know exactly which ad service is to blame https://onetag-sys.com so people can just add that domain to their ad blockers too, some will block it by default as it's one of the domains in https://easylist.to/easylist/easylist.txt

@ShaggyZE Sorry but your suggests did not solve the problem for me. I have added https://onetag-sys.com/ to my blocked list and cleared my cache with no change. Also every one of the files (dozens at this point) downloaded due to this topic have been .htm files of 0 bytes for me.

Perhaps the issue you are experiencing is different than the one I and others are dealing with.

@ArcadiaInferno it's possible, I am using an old version of firefox as well, can you right click any of the downloaded files 0kb or not and find/copy the domain/link, it's possible the issue is happening with other ad services that MAL is using as well.

I also didn't test this theory, I'm only assuming blocking the ad/url/domain would prevent the download, but who knows.
the last time I went to test this (because I use chrome) I couldn't even get it to repeat itself so I assume just working ads were showing during that time.

All of the downloaded files I am getting have a Copy Download Link = about:blank.

@ArcadiaInferno okay, so you'd probably need to open the dev console with F12 and go to the network tab and try to figure out what domain is causing it or possibly what's happening is it is already being blocked by something resulting in the blank file and no "domain/link" so ad blockers wouldn't be able to stop it anyway.

@CC had moz-safe-about in theirs so I checked firefox's forum and found this https://support.mozilla.org/en-US/questions/1375411 it's an older topic, but I guess downloading a http link on a https page (which doesn't seem to be the case for you guys) or links/url/images/code starting with // instead of http or https no longer work (which it never should have worked imo), but regardless on why.

Oh dis happening to others I thought it's my linux bug lol and it's only happening on firefox

@Thewiru

can you open the smug anime girls folder :)