CORS issue for imageboard

[ggw1776]

Description of the issue:
On an image board site (4chan.org), I’m seeing the following error in the console when I navigate to a board, and thumbnail images do not load:
i.4cdn.org/tg/(image ID).jpg:1
GET https://i.4cdn (dot) org/tg/(image ID).jpg net::ERR_BLOCKED_BY_RESPONSE.NotSameOrigin 403 (Forbidden)

And in the network tab:

Exact URL of the website in question:

/tg/ - Traditional Games - 4chan

**Did the issue present with default Shields settings? yes

Does the site function as expected when Shields are turned off? no

Is there a specific Shields configuration that causes the site to break? If so, tell us that configuration. (yes/no): no

Does the site work as expected when using Chrome? no (does work as expected when using firefox)

Brave version (check About Brave):
Version 1.68.137 Chromium: 127.0.6533.100 (Official Build) (64-bit)

NOTE: When I turn on a commercial VPN, the issue does not persist. This issue is consistent across all devices on my network.

[Mattches]

@ggw1776,
Have you tried clearing cache/browsing data for the site? I’m not having any issues seeing images on the site you shared:

You can do this by visiting the site and clicking on the “tune” icon then going to Site Settings --> Delete data:

Also curious if you have any extensions installed at this time?

[ggw1776]

Tried that with no luck, did the same disabling extensions. This is happening on all chromium browsers on my network with different configs (some with fresh brave installations).

[ggw1776]

Speaking of network… tried on 5G on my smartphone and not seeing the issue there. Might be an issue with my ISP?

[Mattches]

It does sound like either a general network issue or perhaps a Chromium issue. Although if you’re viewing the site and images in Brave on 5G then yeah likely more of a network issue.

Are you connected to a VPN at this time? Also are you on your home network or is this a work network/network managed by a company?

[ggw1776]

This is on my home network using a paid VPN service. I’m currently switching between VPN on/off as needed.

[Mattches]

@ggw1776,
Do you see the same results if the VPN is disabled?

[ggw1776]

I’m only seeing the issue if the VPN is disabled. The issue does not persist when the VPN is enabled.

[Mattches]

Sorry, I misread from above. That’s honestly pretty strange. I can try to look into this but as I said previously, if you’re seeing the same results across different browsers then it is likely not an issue specific to Brave. Will let you know what I find out.

[ggw1776]

Appreciated. I’ve tried to do some research on my own but it doesn’t look like anyone else is having this issue; there are a few similar issues I found on stack exchange but no one else has found a root cause.