Week 6, 2026 security incident report

Personal data of 4.62 million Ttareungi members leaked; Seoul Facilities Corporation's response delayed

4.6mImpact: Personal information of about 4.62 million Ttareungi members

The personal information of 4.62 million Ttareungi bike-sharing members was leaked through hacking. It emerged that Seoul Facilities Corporation knew of the leak but took no initial steps such as reporting it, and the Seoul Metropolitan Government asked police to investigate. Victims were subsequently notified individually and compensated with 30-day passes, and some victims filed damages lawsuits.

Ransomware group Qilin claims attack on MBC

Ransomware group Qilin claimed to have attacked MBC. Whether a breach actually occurred, the extent of the damage and MBC's response have not been confirmed.

No action taken after data leak affecting 4.5 million Ttareungyi users

4.5mImpact: Information of 4.5 million users

In 2024, a data leak affecting 4.5 million users occurred at Ttareungyi, a public bike-sharing service. Ttareungyi took no action regarding the leak.

Signs of hack at Yulgok raise fears of KAI partnership documents being exposed

Signs of a hack were raised at aircraft parts maker Yulgok. There are concerns that KAI partnership documents may have been exposed externally, but whether a leak actually occurred, the extent of the damage and the response were not specified.

Signs of personal data leak and hacking traces at Korean Society for Brain and Neural Sciences

Signs of a personal data leak were found at the Korean Society for Brain and Neural Sciences. Traces of hacking were also confirmed, but the scale of the leak and the response have not been disclosed.

Substack user data leaked via exploited API flaw

662.8kImpact: 662,752 user records

An attack exploiting an API flaw at Substack leaked user email addresses, phone numbers and other information. 662,752 user records were published on a cybercrime forum, and Substack notified users of the breach. The incident was discovered about four months after it occurred.

Moltbook security misconfiguration exposes personal data and credentials

Impact: 35,000 email addresses, private messages, API keys and AI agent credentials

A security misconfiguration at Moltbook, a social network for AI agents, exposed user data, API keys and AI agent credentials. Security researchers accessed the database in under three minutes and viewed emails and private messages. The exposed data included 35,000 email addresses.

Cyber-attacks on Italian embassies and Winter Olympics sites thwarted

Cyber-attacks targeted Italian embassies as well as facilities and websites linked to the 2026 Milan-Cortina Winter Olympics. Italy's foreign minister said the attacks had been thwarted and identified the attackers as Russia-linked actors.

Notepad++ hosting breach enables update supply chain attack

Impact: Update supply chain exposed to attack for six months

Notepad++'s hosting infrastructure was compromised and its update channel was abused to distribute malware. It was reportedly exposed to the supply chain attack for six months. The attack was attributed to China-linked state-sponsored hackers.

8.7 billion records including Chinese citizens' personal data leaked

8.7bnImpact: 8.7 billion records including personal data and key corporate information

8.7 billion records, including personal information of Chinese citizens, were leaked. The leaked data also included key corporate information.