  The BL Lacertae (BL Lac) object OJ 287 underwent an intense X-ray activity
phase, exhibiting its brightest recorded X-ray flare in 2016-2017,
characterized by much softer X-ray spectra and, concurrently, its first-ever
recorded very-high-energy (VHE) emission (100--560 GeV), reported by the
VERITAS observatory. Broadband spectral energy distribution reveals a new jet
emission component similar to high-synchrotron-peaked BL Lac objects, thereby
implying the soft X-ray spectrum for the synchrotron emission. Using the
advantage of simultaneous X-ray and VHE spectral information, as well as the
source being a low-synchrotron-peaked BL Lac object, we systematically explored
the extragalactic background light (EBL) spectrum by demanding that the VHE
spectrum cannot be harder than the X-ray spectrum. We used three different
phenomenological forms of the EBL spectral shape (power-law, parabola, and
polynomial) motivated by current constraints on the EBL with the Bayesian Monte
Carlo approach to infer the credible EBL range. Our study favors an almost flat
power-law spectral shape and is consistent with previous studies. The other
spectral forms capable of capturing curvature though result in a better
statistics value; the improvement is statistically insignificant given the
additional parameters.
