curfs ucrfs crufs rcufs urcfs rucfs cufrs ucfrs cfurs fcurs ufcrs fucrs crfus rcfus cfrus fcrus rfcus frcus urfcs rufcs ufrcs furcs rfucs frucs cursf ucrsf crusf rcusf urcsf rucsf cusrf ucsrf csurf scurf uscrf sucrf crsuf rcsuf csruf scruf rscuf srcuf urscf ruscf usrcf surcf rsucf srucf cufsr ucfsr cfusr fcusr ufcsr fucsr cusfr ucsfr csufr scufr uscfr sucfr cfsur fcsur csfur scfur fscur sfcur ufscr fuscr usfcr sufcr fsucr sfucr crfsu rcfsu cfrsu fcrsu rfcsu frcsu crsfu rcsfu csrfu scrfu rscfu srcfu cfsru fcsru csfru scfru fscru sfcru rfscu frscu rsfcu srfcu fsrcu sfrcu urfsc rufsc ufrsc fursc rfusc frusc ursfc rusfc usrfc surfc rsufc srufc ufsrc fusrc usfrc sufrc fsurc sfurc rfsuc frsuc rsfuc srfuc fsruc sfruc
Note: these 'words' (valid or invalid) are all the permutations of the word curfs. These words are obtained by scrambling the letters in curfs.