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aiohttp CookieJar save/load loses host-only flag

Host-only cookies saved with CookieJar.

16 Jun 2026Read 1 minSeverity: schedule it

What changed

Host-only cookies saved with CookieJar.save() and restored with CookieJar.load() lose their host-only status, potentially allowing them to be sent to subdomains that should have been disallowed.

Who it affects

Users of aiohttp who use CookieJar persistence (save/load) and rely on host-only cookie restrictions.

What to do today

Apply the patch from commit a329a7aacad5284f087af36103aff778746da0f2 to fix the issue.

The trail
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