There was a bug in Skype that could cause messages to be sent to incorrect recipients (anyone, not only people from your contact list).

Rails Long Term Support

Rails LTS provides security patches for old versions of Ruby on Rails (2.3, 3.2, 4.2 and 5.2)

• Prevents you from data breaches and liability risks
• Upgrade at your own pace
• Works with modern Rubies

Read more Show archive.org snapshot

If you were using Skype 4 on Linux (or Skype on any other platform), upgrade immediately Show archive.org snapshot .

I don't know if Skype 2 on Linux is affected.