Company
Medical Care Service Co., Ltd.
Medical Care Service Co., Ltd. (Chuo, Saitama, Saitama; Medical care and welfare) appears in 1 related cybersecurity incident. The latest was disclosed on 2026-10-29.
Profile
- Industry/type
- Medical care and welfare
- Location
- Saitama, Saitama, Chuo
- Website
- https://www.mcsg.co.jp/
Public figures
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| Metric | Value | Scope | As of | Source |
|---|---|---|---|---|
| – | ||||
Incident history
Disclosed 2026-10-29Updated 2026-11-10Aichi, Akita, Chiba, Fukui, Fukuoka, Fukushima, Gifu, Gunma, Hokkaido, Hyogo, Ibaraki, Iwate, Kagawa, Kagoshima, Kanagawa, Kochi, Kyoto, Mie, Miyagi, Miyazaki, Nagano, Nagasaki, Niigata, Okayama, Okinawa, Osaka, Saga, Saitama, Shiga, Shizuoka, Tochigi, Tokushima, Tokyo, Toyama, Wakayama, Yamagata, Yamaguchi, Yamanashi[Investigating][Severity: Critical][Through a supplier][Major]
Arara: 81,329,467 email addresses leaked or at risk, affecting up to about 380 clients[Web app exploit][Data leak][Service outage]Leaked 81.3MOrganizations 380
| Incident | Role | Impact level | Methods | Impacts | Status | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
2026-10-29 | 2026-11-10 | 380 Sumitomo Mitsui Banking Corporation, Internet Initiative Japan Inc., Mitsui Fudosan Co., Ltd., Mos Food Services, Inc., Yamanashi Prefecture, AIRDO Co., Ltd., Arara Inc., Asoview Inc., Avance System Co., Ltd., Axel Entermedia Inc., Belc Co., Ltd., Camel Coffee Co., Ltd., Chobirich Inc., DATA X, Inc., Duskin Co., Ltd., GMO MAKESHOP Co., Ltd., GMO Payment Service Inc., Hokuriku Electric Power Company, HR Solutions, Inventit, Japan Leisure Channel Co., Ltd., Java Corporation, Jupiter Golf Network Co., Ltd., Kakaku.com, Inc., Kintetsu Miyako Hotels Inc., Life Corporation, Maker's Shirt Kamakura, Martial Arts Legal Professional Corporation, Matsui Securities Co., Ltd., Monteroza Co., Ltd., NTT TownPage, ODK Solutions, Sakai City, Sasebo City, Shochiku Multiplex Theatres Inc., Solaseed Air Inc., St. Cousair Co., Ltd., Sumitomo Realty & Development Co., Ltd., Takii, TKC Corporation, U Co-op, Workman Co., Ltd., Zaif Inc., Ministry of Internal Affairs and Communications, Tokyo Metropolitan Police Department, City of Sendai, City of Yokohama, Fujitsu Limited, Fukuoka City, JTB Corp., Kawasaki City, Kyoto City, Kyushu Railway Company, Miyazaki Prefecture, Okayama Prefecture, Okinawa Prefectural Government, Osaka City, Osaka Prefectural Government, Osaka Prefectural Police, Saitama Prefecture, Shiga Prefecture, Suzuki Motor Corporation, Yamaguchi Prefecture, Akita Prefecture, Daito City, Edogawa City, Fuji Television Network, Inc., Fukui Prefecture, Fukushima City, Himeji City, Human Academy Co., Ltd., Isahaya City, Isesaki City, Iwata City, The Kagoshima Bank, Ltd., Karatsu City, Kariya City, Kawaguchi City, Kinko's Japan Co., Ltd., Koriyama City, Kumagaya City, Marugame City, Matsudo City, Miyazaki City, Naha City, Nasushiobara City, Nishinomiya City, Odawara City, Okazaki City, Otsu City, SEGA FAVE Corporation, Shimonoseki City, Suzuka City, Takatsuki City, Toda City, Toyama Prefectural Government, Toyohashi City, Utsunomiya City, Yao City, ADS LLC, Aikawa Town, AKASE GROUP Co., Ltd., Akita City, Akita Furusato Mura Co., Ltd., Albait Times Co., Ltd., Asahi Gakken Thinquest Co., Ltd., Asahi Mutual Life Insurance Company, ASOBISYSTEM Co., Ltd., Aya Town, Bank of the Ryukyus, Limited, Barnes de Stroes Japan Limited, Bean Stalk Snow Co., Ltd., BEENOS Entertainment Inc., Bic Camera Inc., BOATRACE Promotion Association, Bunri Co., Ltd., The Chiba Kogyo Bank, Ltd., Chiba Lotte Marines Co., Ltd., Co-op Aichi, Co-op Gifu, Co-op Mie, Congrès Inc., Cosmo Energy Holdings Co., Ltd., CYBIRD Co., Ltd., Densan Co., Ltd., DH Inc., e-CHANNEL Co., Ltd., Echizen Mikuni Boat Race Authority, Ekitan & Co., Ltd., Euglena Co., Ltd., EVENTIFY Inc., Fanplus, Finnovalley Inc., Fire Equipment and Safety Center of Japan, Fujiidera City, Fujinomiya City, Fukui Shimbun Co., Ltd., Fukuoka Chikagai Kaihatsu Co., Ltd., Fukuoka SoftBank Hawks Corp., Furukawa Electric Health Insurance Society, Fussa City, Gakken Cocofump Co., Ltd., Gakken Educational Co., Ltd., Gakken Holdings, Gakken Inc., Gakken LEAP Co., Ltd., Gakken Logistics Co., Ltd., Gakken Medical Support Co., Ltd., Gakken Products Support Co., Ltd., Gakken SEED Co., Ltd., Gakken Smileheartful Co., Ltd., Giftpad Inc., GMO Epsilon, Gold Flag Co., Ltd., Granvista Hotels & Resorts, Grateful Mind Corporation, Hakone Town, Hamanako Boat Race Authority, Hanamaki City, Hasegawa Co., Ltd., Higashikurume City, Higashimurayama Regional Promotion Organization, Hinode Publishing Co., Ltd., Hirano Masakichi Art Foundation, Hokkaido Nippon-Ham Fighters Co., Ltd., Honjo City, Human Resocia, ILL, ING Co., Ltd., Itako City, Itami City, its communications Inc., Iwaki City, Iwamizawa City, Iwate Prefectural University, Japan Digital Laboratory, Japan Society of Civil Engineers, JERA Co., Inc., Joseikan Co., Ltd., The Juhachi-Shinwa Bank, Ltd., Kagoshima Shinkin Bank, Kagoshima Sogo Shinkin Bank, Kainan City, Kaisei Town, Kameyama City, Kanagawa Municipal Employees Mutual Aid Association, Kanagawa Municipal Information System Association, Kanegasaki Town, Kasama City, Kashiwazaki City, Keimix Public Business Co., Ltd., Kintetsu Real Estate Co., Ltd., Kirihara Shoten K.K., Kitamoto City, Kiyosu City, Kobe Shimbun Inc., Kotsu Shimbunsha, Kracie Pharmaceutical, Ltd., Kurihara City, Lee Mills & Company Co., Ltd., LightUp Shopping Club Inc., M.STAGE Co., Ltd., M.STAGE Management Solutions Co., Ltd., Manazuru Town, Manbou Corp., Matsuda Town, MBK Allied Health Insurance Society, Medical Care Service Co., Ltd., Medicus Shuppan, Publishers Co., Ltd., MERY Co., Ltd., Mibu Town, The Minami-Nippon Bank, Ltd., Minkabu The Infonoid, Misato Town (Saitama), Miyoshi Town, Moka City, Motegi Town, Musashimurayama City, Nagakute City, Naka City, Nakai Town, Naruto City, Natural Island Co., Ltd., Natural Science Co., Ltd., NEO CAREER Co., Ltd., Nihon Fukushi University, Ninomiya Town, Nishio City, Nishitetsu Hotels Co., Ltd., Nishitokyo City, Nishiwaki City, Nittobo Health Insurance Society, Nyuzen Town, Obanazawa City, Odakyu Travel Inc., Officemotion Co., Ltd., Oga Aquarium Co., Ltd., Ohtawara City, Oi Town, Oiso Town, Okayama Prefectural Industrial Promotion Foundation, Okinawa Churashima Foundation, Ome City, Osaka Gas Co., Ltd., Pacific League Marketing Corporation, Paris Miki Asset Management Co., Ltd., Rakuten Baseball, Inc., Rakuten Securities, Inc., Ryobi Holdings Co., Ltd., Saitama Parks and Greenery Association, Saito City, Sakai Chamber of Commerce and Industry, Samantha Thavasa Japan Limited, Sanjo City, Sano City, SEGA Corporation, Seibu Lions Co., Ltd., Seijo Ishii Co., Ltd., Setagaya Shopping District Promotion Association Federation, Shimotsuke city, Shioya Town, Shogakukan Inc., Sodegaura City, Sofmap Co., Ltd., Sozo Gakuen Co., Ltd., T-PEC Corporation, Tajimi City, Taka Town, Takanezawa town, Takeda Printing Co., Ltd., Tama Shinkin Bank, Ticketplus, Inc., The Tochigi Bank, Ltd., Toho Cash and Carry, Tokyo Convention & Visitors Bureau, TOKYO GLOBAL GATEWAY Co., Ltd., Tokyo Kantei, Tokyo Marathon Foundation, Tomakomai City, Toyama Prefectural University, Toyoake City, Tribeck Inc., Tsu City, Tsunagu Group Holdings, Ueda City, Ushiku City, Vendome Yamada Co., Ltd., VOLZ, Inc., WATAMI FAST CASUAL MANAGEMENT Co., Ltd., West Japan Packaging Health Insurance Society, WingArc NEX Inc., Yaita City, The Yokohama Rubber Co., Ltd., Yokoshibahikari Town, Yugawara Town, Nagareyama City, Niigata City, AUTHENTIC JAPAN Co., Ltd., ELECOM Co., Ltd., Japan Post Co., Ltd., Kojima Co., Ltd., The Nikkan Kogyo Shimbun, Ltd., Shiki City, Umanity Inc., Warehouse TERRADA, Will Co., Ltd., Itabashi Shopping Street Promotion Association Federation, Maniwa City | Aichi, Akita, Chiba, Fukui, Fukuoka, Fukushima, Gifu, Gunma, Hokkaido, Hyogo, Ibaraki, Iwate, Kagawa, Kagoshima, Kanagawa, Kochi, Kyoto, Mie, Miyagi, Miyazaki, Nagano, Nagasaki, Niigata, Okayama, Okinawa, Osaka, Saga, Saitama, Shiga, Shizuoka, Tochigi, Tokushima, Tokyo, Toyama, Wakayama, Yamagata, Yamaguchi, Yamanashi | 81,329,467 | [Investigating] |