We discovered and fixed a bug in the LINE Developers console that allowed Member users to obtain a channel secret. We sincerely apologize for any inconvenience caused.
On July 24, 2019, we emailed this information to all administrators of channels with Member users.
Issue inception: September 21, 2017
Issue solved: July 17, 2019
There was a bug that allowed Member users to obtain the channel secret, which should have appeared only to Admin users.
The Channel settings tab did not display the channel secret when a Member user viewed the page. However, the API that the LINE Developers console called in the background did return the channel secret. Therefore, a malicious Member user could have obtained and abused the channel secret.
What is a channel secret?
The channel secret is a secret key provided by LINE to call our APIs and validate identities. It should be kept secret from unauthorized parties.
Member user permissions
Originally, Member users can only view basic information and statistics for a channel. They don't have access to the channel secret.
What you should do
If you're concerned that unauthorized Member users have obtained your channel secret, you should issue a new one. Doing so will invalidate the previous channel secret.
After you issue a new channel secret, you'll have to update it in the app which uses the channel secret. Carefully consider the impact of issuing a new channel secret on your app.
How to issue a new channel secret
You can issue a new channel secret on the Channel settings tab in the LINE Developers console.
Forced reissue of channel secret
LINE will not forcibly reissue new channel secrets. The Admin user for each channel should decide whether it's necessary to reissue a new channel secret.
This bug was reported through the LINE Security Bug Bounty Program.
LINE will continue to improve the quality of its services to prevent future outages. Thank you for your understanding.