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Firefox used 14gb foreground data in 5 minutes while on wifi with screen off

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  • Last reply by Seburo

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Hello, I just picked up my phone a few minutes ago and had an alert from the app Glasswire that ALL of my data had been used. My plan renewed yesterday, and I have 10gb of 4g data (then get throttled after). My phone has been sitting on my desk for the last 5 hours, screen off, and connected to wifi.

Glasswire shows that Firefox used up nearly 14gb in less than 5 minutes starting around 11:48am CST. I looked at the app in settings and it shows that all of this data was foreground. While the screen was off. How does that even happen??

This has never ever happened before since I've had Firefox on my phone. It seems like there should be NO WAY it's even possible to use foreground data with the screen off. I certainly didn't do anything with it in all this time today. It takes me an entire month to go through my 4g data and it is all gone in literally 5 minutes.

edit: looking through Glasswire, it appears that Firefox (and only Firefox) ate up about 3-5gb or so starting at roughly 8am til a little after 9:15am. It has used in total 19.6gb in foreground mobile data, while on wifi and the screen turned off- within 6 hours. No other app has any amount of wifi or mobile data access in this timeframe except for a few megs here and there, which is normal for these apps.

Added screenshot from Glasswire.

I have for the moment turned off background data for Firefox in app settings, and denied Firefox access to mobile data using tools within Glasswire. This does not help me with the current problem of using 20gb in less than a day, however.

Attached screenshots

Modified by Jes

All Replies (5)

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Did you have any tabs open that were playing videos or sound, perhaps in an advert?


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Adding this edit here: I'd misread something and didn't actually have the firewall activated for Firefox. It is now properly activated, but I am leaving the original text as-is.

There were tabs open, but I've ALWAYS left my previous tabs and have never had Firefox eating up background data, never. There are no ads because I have uBlock Origin. I also have a "no coin mining" add-on and "Only audio for YouTube" add-on, both of which remain on their previous settings. The YouTube audio only app was not turned on, and I've actually never needed to use it yet, but it's been on my phone for a few months. Nothing whatsoever was changed between today and yesterday, or between today and the last 4+ months. YouTube cannot play in a background tab on mobile, it is functionally disabled from doing so without special add-ons or apps, and I'd have heard the audio if it did because my phone was two feet away.

This is the tab I had open. I do not receive any ads because of uBlock Origin, but I'm including it just because, in case anyone asks;

There were also no unusual links in my history, everything was exactly what I'd expect.

I DO have sync turned on, as I use Firefox exclusively on my desktop computer, but again there has never been anything like this happening before in I guess about 6 months or more that I've had sync turned on, and I can't think of any way sync would suddenly make my mobile phone just start eating data out of nowhere when it's never happened before.

Additionally, it appears that Firefox has eaten yet another 5gb of data while I was asleep. This while in app settings I had restrict background data turned on, AND blocked its access to mobile data in Glasswire!

The only, and I mean only thing I can think of is that I'm on Virgin Mobile, which is migrating all customers over to a new service because they are ending Virgin Mobile, but I cannot imagine how it's possible that that would have anything to do with Firefox specifically. If the migration somehow affected my phone (and why would it use data instead of wifi anyway?) the data would show up in a system-based app instead of a specific browser, but I guess weirder things have happened.

At this point, I will be force-quitting and disabling Firefox until I specifically want to use it. Thank God my data only gets throttled instead of being charged enormous fees because I'd never afford paying for this.

Modified by Jes


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Since making sure my firewall was turned on (I was trying to deal with this immediately after waking up yesterday so wasn't paying close enough attention to it) I have not seen Firefox access wifi or mobile data.

I still have no explanation how in the world it even USED 25gb foreground data while the phone screen off, or why it'd access mobile data when connected to wifi. I will be monitoring it closely for anything else happening.


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Okay, well I guess we can close this. After spending a while (a couple hours) faffing around with apps, disabling and enabling things, changing settings, and scouring help sites, I have figured out that the listed data used was incorrect, both in Glasswire AND my app listing in my phone settings. Both showed 25gb usage. However I was finally able to log into my migrated mobile account since I hadn't been able to access it for several days. According to my dashboard, my account has only registered 0.7gb, even tho my phone is convinced it used 25gb of data.

Panic averted I guess, thankfully! I still have no explanation on why my phone recorded that data as clearly it was false. I am really glad tho because I love Firefox and I've been using it over 10 years, and really did not want to change browsers.

In the mean time, just to be cautious, I'm keeping the data restrictions on until I'm actually using it.

Thanks for the attempt to help me. This is kinda embarrassing now, but there you go. Maybe someone else will see this after a similar issue, maybe something will be helpful.


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No problem, I am just glad that this has been resolved.

Thank you for your support of Firefox an for letting us know this has been fixed.


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