  DE Boo is a unique system, with an edge-on view through the debris disk
around the star. The disk, which is analogous to the Kuiper belt in the Solar
System, was reported to extend from 74 to 84 AU from the central star. The high
photometric precision of the Characterising Exoplanet Satellite (CHEOPS)
provided an exceptional opportunity to observe small variations in the light
curve due to transiting material in the disk. This is a unique chance to
investigate processes in the debris disk. Photometric observations of DE Boo of
a total of four days were carried out with CHEOPS. Photometric variations due
to spots on the stellar surface were subtracted from the light curves by
applying a two-spot model and a fourth-order polynomial. The photometric
observations were accompanied by spectroscopic measurements with the 1m RCC
telescope at Piszk\'estet\H{o} and with the SOPHIE spectrograph in order to
refine the astrophysical parameters of DE Boo. We present a detailed analysis
of the photometric observation of DE Boo. We report the presence of nonperiodic
transient features in the residual light curves with a transit duration of
0.3-0.8 days. We calculated the maximum distance of the material responsible
for these variations to be 2.47 AU from the central star, much closer than most
of the mass of the debris disk. Furthermore, we report the first observation of
flaring events in this system. We interpreted the transient features as the
result of scattering in an inner debris disk around DE Boo. The processes
responsible for these variations were investigated in the context of
interactions between planetesimals in the system.
