Without access to more data, it's difficult to pronounce this true or false. The article does say:
For the period September 2001 through 2014, data shows the U.S. successfully prosecuted 580 individuals for terrorism and terror-related cases. Further, since early 2014, at least 131 individuals were identified as being implicated in terror.
Across both those groups, the senators reported that at least 40 people initially admitted to the U.S. as refugees later were convicted or implicated in terror cases.
Among the 580 convicted, they said, at least 380 were foreign-born. The top countries of origin were Pakistan, Lebanon and Somalia, as well as the Palestinian territories.
The 380 foreign-born convicts heavily over-represent the Middle East. But, apparently only about 10% were considered "refugees".
This is why parsing the sentence carefully is necessary. If you confine the discussion to "refugees", the results are much different than considering all immigrants from majority Islamic countries.
Exactly. But we can say that the majority of terrorists were foriegn born Islamists. So Islamic refugees are more likely to be terrorists than Tibetan monks.