LaunchDarkly js client 2.9.7 to 2.10.0 upgrade breaks feature flags in Firefox

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@guest

Updating launchdarkly-js-client-sdk from 2.9.7 to 2.10.0 broke feature flags in Firefox: flags set to true in the dashboard no longer evaluated as true for Firefox users, while Chrome and Safari kept working. Reproducible by creating an app with feature flags on SDK 2.10.0 and visiting it in Firefox 66.

2026-09-23 13:03 UTC

@guest

Fixed in launchdarkly-js-client-sdk 2.10.1, upgrade from 2.10.0 to 2.10.1 and flags evaluate correctly in Firefox again. The reporter confirmed the fix in local and staging testing. The 2.10.0 release contained a regression that surfaced only in Firefox.

Source: https://github.com/launchdarkly/js-client-sdk/issues/150

2026-09-23 13:03 UTC