update: Note Tor Browser security level flaw (#3026)

Signed-off-by: redoomed1 <redoomed1@privacyguides.org>
Signed-off-by: Freddy <freddy@privacyguides.org>

Author: jonaharagon

docs/desktop-browsers.md

@@ -88,7 +88,11 @@ If you need to browse the internet anonymously, you should use [Tor](tor.md) ins
 
 </div>
 
-Like [Tor Browser](tor.md), Mullvad Browser is designed to prevent fingerprinting by making your browser fingerprint identical to all other Mullvad Browser users, and it includes default settings and extensions that are automatically configured by the default security levels: *Standard*, *Safer* and *Safest*. Therefore, it is imperative that you do not modify the browser at all outside adjusting the default [security levels](https://tb-manual.torproject.org/security-settings). Other modifications would make your fingerprint unique, defeating the purpose of using this browser. If you want to configure your browser more heavily and fingerprinting is not a concern for you, we recommend [Firefox](#firefox) instead.
+Like [Tor Browser](tor.md), Mullvad Browser is designed to prevent fingerprinting by making your browser fingerprint identical to all other Mullvad Browser users, and it includes default settings and extensions that are automatically configured by the default security levels: *Standard*, *Safer* and *Safest*.
+
+Therefore, it is imperative that you do not modify the browser at all outside adjusting the default [security levels](https://tb-manual.torproject.org/security-settings). When adjusting the security level, you **must** always restart the browser before continuing to use it. Otherwise, [the security settings may not be fully applied](https://www.privacyguides.org/articles/2025/05/02/tor-security-slider-flaw/), putting you at a higher risk of fingerprinting and exploits than you may expect based on the setting chosen.
+
+Modifications other than adjusting this setting would make your fingerprint unique, defeating the purpose of using this browser. If you want to configure your browser more heavily and fingerprinting is not a concern for you, we recommend [Firefox](#firefox) instead.
 
 ### Anti-Fingerprinting
 

docs/tor.md

@@ -80,7 +80,7 @@ You should **never** install any additional extensions on Tor Browser or edit `a
 
 </div>
 
-The Tor Browser is designed to prevent fingerprinting, or identifying you based on your browser configuration. Therefore, it is imperative that you do **not** modify the browser beyond the default [security levels](https://tb-manual.torproject.org/security-settings).
+The Tor Browser is designed to prevent fingerprinting, or identifying you based on your browser configuration. Therefore, it is imperative that you do **not** modify the browser beyond the default [security levels](https://tb-manual.torproject.org/security-settings). When modifying the security level setting, you **must** always restart the browser before continuing to use it. Otherwise, [the security settings may not be fully applied](https://www.privacyguides.org/articles/2025/05/02/tor-security-slider-flaw/), putting you at a higher risk of fingerprinting and exploits than you may expect based on the setting chosen.
 
 In addition to installing Tor Browser on your computer directly, there are also operating systems designed specifically to connect to the Tor network such as [Whonix](desktop.md#whonix) on [Qubes OS](desktop.md#qubes-os), which provide even greater security and protections than the standard Tor Browser alone.
 
@@ -110,5 +110,3 @@ In addition to installing Tor Browser on your computer directly, there are also
 Onion Browser does not provide the same levels of privacy protections as Tor Browser does on desktop platforms. For casual use it is a perfectly fine way to access hidden services, but if you're concerned about being traced or monitored by advanced adversaries you should not rely on this as an anonymity tool.
 
 [Notably](https://github.com/privacyguides/privacyguides.org/issues/2929), Onion Browser does not *guarantee* all requests go through Tor. When using the built-in version of Tor, [your real IP **will** be leaked via WebRTC and audio/video streams](https://onionbrowser.com/faqs) due to limitations of WebKit. It is *safer* to use Onion Browser alongside [Orbot](alternative-networks.md#orbot), but this still comes with some limitations on iOS.
-
-[^1]: The `IsolateDestAddr` setting is discussed on the [Tor mailing list](https://lists.torproject.org/pipermail/tor-talk/2012-May/024403.html) and [Whonix's Stream Isolation documentation](https://whonix.org/wiki/Stream_Isolation), where both projects suggest that it is usually not a good approach for most people.