Rulings
Q1: What happens to cards placed face up in the security stack by effects?
They become face-up security cards that remain revealed. Other than rules that specify face-up security cards, the rules apply in the same manner as standard security cards.
Q2: What happens upon a security check for a security card that is placed face-up?
The check is performed with the card left revealed. Other than rules for cards left revealed, the rules apply in the same manner as standard security checks.
Q3: Does a card's Security effect trigger upon a security check with that card placed face-up?
Yes, it triggers.
Q4: What happens if I shuffle a security stack that includes security cards placed face-up?
Any face-up cards are placed face down, then you shuffle the cards. After shuffling, all cards are left face-down.
Data Sources
Island of Adventure ST20-15 U ADVENTURE While you have no face-up [Island of Adventure] security cards, you can ignore this card's color requirements. [Security] [All Turns] All of your level 3 or higher Digimon get +2000 DP. [Main] Add your top security card to the hand. Then, place this card face up as the top security card. --- [Security] You may play 1 Tamer card from your hand without paying the cost.
Island of Adventure ST20-15 U ADVENTURE While you have no face-up [Island of Adventure] security cards, you can ignore this card's color requirements. [Security] [All Turns] All of your level 3 or higher Digimon get +2000 DP. [Main] Add your top security card to the hand. Then, place this card face up as the top security card. --- [Security] You may play 1 Tamer card from your hand without paying the cost.
Island of Adventure ST20-15 U ADVENTURE While you have no face-up [Island of Adventure] security cards, you can ignore this card's color requirements. (Security) [All Turns] All of your level 3 or higher Digimon get +2000 DP. [Main] Add your top security card to the hand. Then, place this card face up as the top security card. ---