Mozilla said last week it would delete all telemetry data collected because of a bug in the Firefox crash reporter.

According to Mozilla engineers, Firefox has been collecting information on crashed background tabs from users' browsers since Firefox 52, released in March 2017.

Firefox versions released in that time span did not respect user-set privacy settings and automatically auto-submitted crash reports to Mozilla servers. The browser maker fixed the issue with the release of Firefox 57.0.3.

Crash reports are not fully-anonymized

Crash reports are not fully-anonymized. According to Mozilla's Privacy Policy, "crash reports include the active URL at time of crash," and also "include a ‘dump file’ of Firefox’s memory contents at the time of the crash, which may contain data that identifies you or is otherwise sensitive to you."

Depending on the URL of the crashed tab, this data may tie crash reports back to individual users.

Because of the privacy implications regarding the accidental collection of data from users who did not agree to share the reports, Mozilla decided to delete all crash reports it received since Firefox 52 when the bug was introduced in the Firefox codebase.

Mozilla engineers took this step because they could not "distinguish between users that chose to auto-submit crashes and users that triggered the bug."

Decision to delete crash reports is a pretty big deal

This is a huge decision as it leaves the Mozilla team with no telemetry data about Firefox crashes for the last nine months.

Furthermore, engineers have also modified Mozilla servers to refuse auto-submitted crash reports from all Firefox versions between v52 and v57.0.2, as they could not tell which came from browsers where users selected the option to auto-submit crash reports, and which came from browsers affected by the bug.

In an age where companies don't seem to care about user security, let alone privacy, Mozilla's decision to delete crucial telemetry to safeguard user privacy is commendable.

Below is an image of the Firefox option that controls if Firefox auto-submit bug reports to Mozilla.