Twitter on Thursday urged its more than 300 million users to change their passwords, saying they had been unintentionally “unmasked” inside the company by a software bug.
Japan Today

HINTS
S Twitter ([on] Thursday)
V [urged] 急き立てる
O its more than 300 million users
V [to change]
O their passwords
,

補足
[saying]

S they
V [had been]
O unintentionally “unmasked” 意図されず
inside the company 社内で
補足
[by] a software bug. ソフトウェアのバグによって