Possible endless loop in cookie.js

[stefan-maximilian]

Prerequisites

• I verified that this is not a filter list issue. Report any issues with filter lists or broken website functionality in the uAssets issue tracker.
• This is NOT a YouTube, Facebook or Twitch report. These sites MUST be reported by clicking their respective links.
• This is not a support issue or a question. For support, questions, or help, visit /r/uBlockOrigin.
• I performed a cursory search of the issue tracker to avoid opening a duplicate issue.
• The issue is not present after disabling uBO in the browser.
• I checked the documentation to understand that the issue I am reporting is not normal behavior.

I tried to reproduce the issue when...

• uBO is the only extension.
• uBO uses default lists and settings.
• using a new, unmodified browser profile.

Description

The scriptlets set-cookie-reload and trusted-set-cookie-reload (registered in
src/js/resources/cookie.js) set a cookie on the client side and then call
window.location.reload().

There is an existing early-exit check (line 122):

if ( cookieBefore === value && options.reload ) { return; }

However, this only prevents a reload if the cookie already had the correct value before
being set. If the server discards or overwrites the cookie after the reload, this condition
will not match on the next scriptlet run – triggering yet another reload, resulting in an
infinite loop.

A specific URL where the issue occurs.

The issue is not tied to a single URL. It can occur on **any website** where:
- a filter rule using `set-cookie-reload` or `trusted-set-cookie-reload` is active, **and**
- the server discards or overwrites the cookie set by the scriptlet on each request.

Example filter rule that triggers the issue:

example.com##+js(set-cookie-reload, consent, accepted)

Steps to Reproduce

1. Find or create a page whose server removes/overwrites a specific cookie on every request.
2. Add a uBlock Origin filter rule using set-cookie-reload targeting that cookie:

   example.com##+js(set-cookie-reload, consent, accepted)
   

3. Open the page in the browser.
4. Observe the browser entering an infinite reload loop:
   • Scriptlet sets the cookie client-side → done = true → window.location.reload() is called
   • Server discards the cookie during the request
   • Page reloads → cookie is missing → early-exit check (line 122) does not trigger
   • Scriptlet sets the cookie again → another reload → …

Expected behavior

The number of reloads should be limited (e.g. 2–3 attempts). If the cookie still does not
hold the expected value after those attempts (because the server keeps discarding it), no
further reload should be triggered.

Troubleshooting information

- **Affected file:** `src/js/resources/cookie.js` – function `setCookieFn`
- **Affected scriptlets:** `set-cookie-reload` (line 239), `trusted-set-cookie-reload` (line 333)
- **Severity:** High – the browser gets stuck in an infinite reload loop, making the page
  completely unusable
- **uBlock Origin version:** uBlock-master, as of April 2026
- **Affected browsers:** All (Chromium, Firefox)

[gorhill]

If there are cases of infinite reload, then the filter needs to be fixed, there is no way for uBO to keep count of the reloads. It could use a dedicated entry in the site's local storage, but this means leaking uBO information to the site, which is to be avoided. Just report the specific sites suffering the reload issue using "Report an issue..." in the popup panel.

---

To avoid reload when the cookie is already set, use dontOverwrite:

example.com##+js(set-cookie-reload, consent, accepted, , dontOverwrite, 1)

So closing as an unspecific filter issue. Report specific filter issues to filter maintainers at https://github.com/uBlockOrigin/uAssets repo.

[krystian3w]

It was already:

#3984

Perhaps it would be useful to suggest opening problems in discussions, e.g. 18+ boards that reload pages until address in filter #3155