Some of the user accounts of Telecom’s YahooXtrahas had their details compromised, following a security breach, which apparently affected non-Telecom customers as well.
Apparently, Yahoo acknowledged an email security breach that compromised some YahooXtra email accounts.
Source: https://www.databreaches.net/yahooxtra-email-accounts-compromised-following-security-breach/
"id": "YAH228141222",
"linkid": "yahoo",
"type": "Breach",
"date": "01/2014",
"severity": "100",
"impact": "4",
"explanation": "Attack with significant impact with customers data leaks"