Gissur's Note

Can be obtained from the body of Gissur, a spy walking around The Ragged Flagon during the quest A Cornered Rat.

Text:

"Description of target:

 Character race and gender , believed to go by character name (may be an alias). Likely to be inquiring about "Esbern" and the Ratway.

Do not approach. Inform your assigned contact immediately if spotted."

It is unclear what purpose Gissur may serve; he may be an agent of the Thalmor.