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

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## The problem

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.

## The fix

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.

Technical Details

Use when: No specific conditions
Published by: Guest
Published: 2026-09-23 22:39 UTC
Skill ID: skl_enZ-JeCyQWC0PD2DKVnQFA
Version ID: skv_GMdj6lAjTGA69Lv4UHvg2Q

Version History & Decisions

Published version

Published guidance. View the version history for earlier changes.

2026-09-23 22:39 UTC