XTB, one of Europe's largest publicly listed brokers (WSE: XTB), experienced a major platform failure yesterday (Wednesday) that prevented clients from closing positions for several hours, leaving traders exposed to market movements without the ability to manage their risk.

However, the company’s shares at today's (Thursday’s) open did not show a sharp negative reaction to the recent run of problems, falling 0.7% and testing 70.92 zlotys.

XTB Platform Outage Blocks Position Closures During Trading Hours

The problems started around 4 p.m. local time when users began reporting they could open new positions but couldn't close existing ones. The issue persisted through the evening, with XTB announcing at 10 p.m. that all CFD trading would be suspended between 10 p.m. and 11 p.m. while engineers attempted repairs.

"We are informing you that due to problems in the functioning of our investment platform and in order to repair the technical fault, trading on CFD instruments between 22-23 will be impossible," the company said in a statement on its website. "We will keep you informed about the progress of this work on an ongoing basis. We apologize for the inconvenience."

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After the scheduled maintenance window, users could again open positions but still couldn't close them, extending the lockout well past midnight.

The problems come shortly after XTB reported a sharp decline in net profit for the third quarter - one of its weakest results since late 2022.

No Clear Timeline for Resolution

By late Wednesday evening, XTB had not explained what caused the failure or when normal operations would resume. The company's silence left traders guessing about the technical root cause and their potential losses from being unable to react to market swings.

Social media filled with speculation about the source of the problem. One theory gaining traction among technical observers suggested the platform hit a programming limit known as integer overflow, where a counter tracking transaction IDs exceeded the maximum value a standard 32-bit integer can hold.

A user posting on X under the handle kwit_flip wrote that XTB "just rolled over its INT," referring to the 4-byte integer data type. "That's why you can't close positions right now," the user claimed, noting that transaction numbers had wrapped from positive to negative values after hitting roughly 2.1 billion.

XTB właśnie przekręciło INT'a.

To jest rozmiar 4-bajtowego INTEGERA - to typ danych, którym zapisywane są transakcje na platformie @xtb. Dziś został przekroczony dodatni maksymalny numer transakcji i mamy ujemne wartości.

Dlatego nie da się w tej chwili zamknąć pozycji. pic.twitter.com/MPL4Tvj5Oe

— kwitflip (@kwit_flip) November 5, 2025

The theory remained unverified by the company.

Recent Track Record Under Scrutiny

The outage marks the latest in a series of technical problems at XTB. In a recent interview with Parkiet, board member Filip Kaczmarzyk acknowledged past platform issues while defending the company's progress.

"Of course there were moments when the platform did not work as it should, and such situations have no right to happen," Kaczmarzyk said. "It is a problem for all of us, not just for clients. However, it is definitely not the case that we only look at the platform when something bad happens. Compared to what it was two or three years ago, we have also made really huge progress."

The timing proved particularly awkward for XTB, which just days earlier announced a record 100,000 new clients in October. The company now faces questions about whether its infrastructure can handle its rapidly growing user base.

Data from Downdetector showed a sharp spike in problem reports between 4 p.m. and midnight Wednesday, then dropping to near zero afterward. On Thursday morning, however, a slight upward trend is visible again:

"So you're saying you have a product you make the most money on, where client reaction time is measured in seconds and minutes because they're trading on leverage, but at the same time your product doesn't work for them for two hours and they can't do anything with open positions?" wrote one X user.

XTB has not yet addressed whether it will compensate clients who suffered losses during the outage or clarified the complaints process mentioned by customer service representatives.

Another Issue Following the August Hack

Given that XTB refunded client losses in August after the alleged 150,000 zloty hack drew wide attention, some investors may hope that the latest case will lead to a similar outcome.

The announcement came amid renewed pressure after the latest victim’s account gained traction on local financial forums and media outlets. The client described how hackers allegedly carried out simultaneous buy and sell orders on thinly traded securities, leaving his account consistently in loss while a separate account captured the gains. The incident has again raised questions about the platform’s security and investor protection standards.