Issue watchers continue receiving updates even after their Jira account is revoked - CVE-2021-39119

h3. Summary

Affected versions of Atlassian Jira Server and Data Center allow users who have watched an issue to continue receiving updates on the issue even after their Jira account is revoked, via a Broken Access Control vulnerability in the issue notification feature.

The affected versions are before version 8.19.0.
h4. Affected versions:

• version < 8.19.0

h4. Fixed versions:

• 8.19.0

h4. Note on fix

Due to this change, Jira notifications (batched and non-batched) not sent anymore to users who don’t have application access after Jira upgrade to 8.19.0, see [related KB|https://confluence.atlassian.com/jirakb/jira-notifications-batched-and-non-batched-not-sent-anymore-to-some-users-after-jira-upgrade-to-8-19-0+-1096091978.html] and suggestion JRASERVER-73165.

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Since Jira 8.20.6 it will be possible to revert new behaviour introduced by JRASERVER-72737 with [Dark Feature Flag|https://confluence.atlassian.com/jirakb/enable-dark-feature-in-jira-959286331.html]:
{code:java}
com.atlassian.jira.send.email.notifications.to.user.without.application.access.enabled {code}
At the same time 8.13.19+ will have option to enable new fix with feature flag:
{code:java}
com.atlassian.jira.send.email.notifications.to.user.without.application.access.enabled {code}
Cheers,
Jira DC Bugfix Team
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