LONDON, July 24 (Reuters) - A CrowdStrike ( CRWD )

software update that crashed computers globally last week

hitting services from aviation to banking and healthcare was

caused by a bug in the U.S. cybersecurity firm's quality control

mechanism, the company said on Wednesday.

Friday's outage happened because CrowdStrike's ( CRWD ) Falcon

Sensor, an advanced platform that protects systems from

malicious software and hackers, contained a fault that forced

computers running Microsoft's ( MSFT ) Windows operating system

to crash and show the "Blue Screen of Death".

"Due to a bug in the Content Validator, one of the two

Template Instances passed validation despite containing

problematic content data," CrowdStrike ( CRWD ) said in a statement,

referring to the failure of an internal quality control

mechanism that allowed the problematic data to slip through the

company's own safety checks.

CrowdStrike ( CRWD ) did not say what that content data was, nor why

it was problematic. A "Template Instance" is a set of

instructions that guides the software on what threats to look

for and how to respond. CrowdStrike ( CRWD ) said it had added a "new

check" to its quality control process in a bid to prevent the

issue from occurring again.

The extent of the damage from the botched update is still

being assessed. On Saturday, Microsoft ( MSFT ) said about 8.5 million

Windows devices had been affected, and the U.S. House of

Representatives Homeland Security Committee has sent a letter to

CrowdStrike ( CRWD ) CEO George Kurtz asking him to testify.

CrowdStrike ( CRWD ) released information to fix affected systems

last week, but experts said getting them back online would take

time as it required manually weeding out the flawed code.

Wednesday's statement was in line with a widely held

assessment from cybersecurity experts that something in

CrowdStrike's ( CRWD ) quality control process had gone badly wrong.