Hacker Claims GMO Ignored Dozens of Vulnerability Reports — 5ch Reacts: ‘That’s Just Incompetent’

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The story

A story blew up on 5ch after a hacker claimed they had reported vulnerabilities to GMO’s security contact point dozens of times over several months, only to be ignored. GMO Group operates widely across payment processing and internet-related services, putting it in a position where neglecting such reports could have real consequences for how customer data is handled. The thread split between users slamming the company’s inaction as sheer incompetence and others questioning the hacker’s motives and methods, while reactions also spread over executives who had posted selfies right after the scandal broke.

What people said

2AnonymousOct 28, 2026 12:17
This basically makes him sound like a righteous hacker, doesn't it 😢
10AnonymousOct 28, 2026 12:21
Time to wake them up
(though apparently he's now using customer data as leverage to demand money
24AnonymousOct 28, 2026 12:28
Re: #10
If there was no reward on the table, why would he even bother reporting the vulnerability in the first place
The real problem is GMO being a bunch of cheap f**kers…
30AnonymousOct 28, 2026 12:29
Re: #10
The person who reported the bug to GMO and the person making threats now are two different people
Only Yahoo Comments readers and the 'NanJ' board crowd (known for skimming without reading) could fail to parse something this simple
15AnonymousOct 28, 2026 12:23
The 'white hat hacker' defense, right on schedule
22AnonymousOct 28, 2026 12:27
Re: #15
More like a 'white f**ker'
16AnonymousOct 28, 2026 12:24
It's hilarious how hard the CEO is working to spread personal info around
19AnonymousOct 28, 2026 12:25
Start by exposing the CEO and the execs — why go after the customers first
20AnonymousOct 28, 2026 12:26
The moment he doxxed people, any claim to being 'righteous' went out the window
21AnonymousOct 28, 2026 12:27
Maybe he couldn't read English, or couldn't understand what was being pointed out?
But that seems unlikely when they supposedly have 200 people on staff
23AnonymousOct 28, 2026 12:28
Kinda makes me see him differently now — like a yakuza who actually protects the town
26AnonymousOct 28, 2026 12:28
So it went: 'I found a vulnerability, pay up' → ignored → turned into blackmail? Being too cheap to pay and letting it blow up like this is just incompetent
27AnonymousOct 28, 2026 12:28
A ransom of 150 million yen is way too low for this
28AnonymousOct 28, 2026 12:29
And they supposedly had 200 white hat hackers on staff 😢

tps://i.imgur.com/UbDeqpF.jpeg
tps://i.imgur.com/AuvC9dj.jpeg
tps://i.imgur.com/ZprzGUm.jpeg
tps://i.imgur.com/aT2DhHP.jpeg
43AnonymousOct 28, 2026 12:33
Re: #28
Whether management actually acts on a report is a whole separate issue — every time
85AnonymousOct 28, 2026 12:55
Re: #28
No different from some fake engineer who's really just a crappy YouTuber
90AnonymousOct 28, 2026 13:00
Re: #28
These guys are all staring at the same kind of weird-looking screen
Is that actually meaningful, or just for show?
29AnonymousOct 28, 2026 12:29
Isn't there a theory that the person who got doxxed is actually someone connected to GMO?
31AnonymousOct 28, 2026 12:31
GMO probably treats engineers like disposable errand boys
49AnonymousOct 28, 2026 12:37
Later the CEO's gonna say 'well, it ended up being great publicity' and you'll have officially lost
82AnonymousOct 28, 2026 12:54
Re: #49
No matter how this turns out, I'm never using GMO again
50AnonymousOct 28, 2026 12:38
You guys sure believe whatever a hacker says pretty easily
51AnonymousOct 28, 2026 12:39
Re: #50
Well, a hacker's word carries more weight than an idiot's
55AnonymousOct 28, 2026 12:42
Re: #50
And they really did get hacked and are freaking out, so…
57AnonymousOct 28, 2026 12:42
I don't want to hear a word from someone who's grinning and taking selfies at a time like this
https://x.com/m_kumagai/status/2115085981695222149?a=_B81VGJAzCgEr0NoVoM&s=19
62AnonymousOct 28, 2026 12:43
Re: #57
What's he even laughing about
67AnonymousOct 28, 2026 12:46
Assemble

70AnonymousOct 28, 2026 12:48
Re: #67
Protecting what, from what, exactly?
76AnonymousOct 28, 2026 12:52
If you guys ever managed to get unauthorized access somewhere
you'd go straight for some celebrity's personal info first, right?
This hacker clearly doesn't understand Japan — must be a foreigner
84AnonymousOct 28, 2026 12:55
Re: #76
Even without understanding Japan, you'd still dig up stuff on celebrities and politicians
Though maybe it's the opposite — he avoided them precisely because he does understand
80AnonymousOct 28, 2026 12:54
That's just the kind of company culture they have
They probably don't spend money on security
They probably just dump it on the police and the Self-Defense Forces and run
83AnonymousOct 28, 2026 12:54
Re: #80
Because handing it off to the government costs nothing
87AnonymousOct 28, 2026 12:56
Re: #80
By the way, a former senior Self-Defense Forces official parachuted into a cushy post there
I bet they're behind the strategy for how this whole thing's being handled

Background and key points of this story

‘Responsible disclosure’ — where someone who finds a vulnerability reports it directly to a company — is often backed by formal bug bounty programs at major overseas tech firms. When a report gets delayed or ignored, it’s not uncommon for the reporter to go public or, as in this case, for things to escalate into a full-blown controversy. Within the thread, some replies pointed out that the person who originally reported the vulnerability to GMO and the person now allegedly demanding money using customer data are two different individuals, though several posts conflated the two. It’s worth noting that everything shared here comes from one-sided accounts by anonymous posters, and as of this thread, GMO has not issued any official statement or confirmed the facts.

※This article is excerpted and summarized from the 5ch (Nandemo Jikkyō G) thread「[Sad News] GMO Hacker: ‘I Reported to GMO’s Vulnerability Contact Dozens of Times Over Several Months, But Was Ignored’」.

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